Lithographic printing plate precursors and processes for preparing lithographic printing plates

ABSTRACT

Provided is lithographic printing plates and processes for preparing the lithographic printing plates having excellent printing durability, staining resistance and staining resistance over time. 
     A lithographic printing plate precursor comprising: a substrate; a photosensitive layer provided on the substrate; and an extra layer optionally provided between the substrate and the photosensitive layer; wherein the photosensitive layer or the extra layer adjacent to the substrate contains (A) a copolymer; and wherein the copolymer (A) comprises: (a1) a repeating unit having a structure represented by formula (a1-1) below in a side chain, and (a2) a repeating unit having at least one of the structures represented by formulae (a2-1) to (a2-6) below in a side chain. L 1  represents a single bond, a divalent aromatic group containing 6 to 14 carbon atoms, —C(═O)—O—, or —C(—0)═NR 2 — (wherein R 2  represents a hydrogen atom, alkyl or aryl). Z 1  represents methylene, ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, cyclohexane-1,4-diyl, 1,2-phenylene, 1,3-phenylene, 1,4-phenylene, 1,2-naphthalene, 1,5-naphthalene and a linking group composed of two or more of these divalent linking groups linked through —O— or —S—, wherein a hydrogen atoms in these divalent linking groups may be replaced by substituents. R 1  represents a hydrogen atom, alkyl, aryl, heterocyclyl, sulfo, alkylsulfonyl and arylsulfonyl. R 21 , R 22  and R 23  each independently represent a hydrogen atom, halogen atom or C1-8 alkyl.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of PCT/JP2012/054056 filed onFeb. 21, 2012 and claims priority under 35 U.S.C. §119 of JapanesePatent Application No. 042496/2011, filed on Feb. 28, 2011, JapanesePatent Application No. 042497/2011, filed on Feb. 28, 2011, and JapanesePatent Application No. 013295/2012, filed on Jan. 25, 2012, the contentof which are herein incorporated by reference in their entirety.

FIELD OF THE INVENTION

The present invention relates to a lithographic printing plate precursorand a method of manufacturing a lithographic printing plate, accordingto which a printing plate is directly manufacturable based on digitalsignal output from a computer or the like using various types of laser,the technique being so-called direct plate making, and particularly to alithographic printing plate precursor and a method of manufacturingplanographic a printing plate suitable for simplified processes.

DESCRIPTION OF THE RELATED ART

Solid-state laser, semiconductor laser, and gas laser capable ofemitting ultraviolet radiation, visible light and infrared radiation,over a wavelength range of 300 nm to 1200 nm, have been becoming morereadily available in larger output and smaller size, and these types oflaser are very important as recording light sources in direct platemaking process using digital data output from a computer or the like.Various recording materials sensitive to these types of laser light havebeen investigated. The first category of the materials are thoseadaptive to infrared laser recording at an image recording wavelength of760 nm or longer, which are exemplified by positive recording material(Patent Document 1), and negative recording material causingacid-catalyzed crosslinking (Patent Document 2). The second category ofthe materials are those adoptive to ultraviolet or visible light laserrecording over the wavelength range from 300 nm to 700 nm, which areexemplified by radical-polymerizable negative recording material(Patent. Document 3, Patent Document 4).

The conventional lithographic printing plate precursor (also referred toas “PS plate”, hereinafter) have essentially needed, after exposure forimage forming, a process of solubilizing and removing thenon-image-forming area using an aqueous strong alkaline solution(development process), and have also needed water washing of thedeveloped printing plate, rinsing with a rinsing solution containing asurfactant, and post-treatment such as using a desensitization solutioncontaining gum arabic or a starch derivative. Indispensableness of theseadditional wet processes has been a big issue of the conventional PSplate. This is because, even if the former half of the plate makingprocess (pattern-wise exposure) may be simplified by virtue of digitalprocessing, the effect of simplification is limitative so long as thelatter half (development process) relies upon such labor-consuming wetprocess.

In particular in recent years, friendliness to the global environmenthas been a great matter of interest across the whole area of industry,so that issues to be solved from the environmental viewpoint include useof a developer more close to neutral, and reduction in volume of wasteliquid. Among others, the wet post-treatment have been desired to besimplified, or replaced with a dry process.

From this point of view, there has been known methods of simplifying thepost-treatment process, exemplified by single-liquid treatment orsingle-bath treatment, by which development and gum solution areproceeded at the same time. More specifically, they belong to a sort ofsimplified development process by which the original plate is exposedpattern-wise without pre-water washing; removal of a protective layer,removal of the non-image-forming area, and coating of gum solution areimplemented concomitantly using a single solution or in a single bath;the original plate is dried without post-water washing, and then putinto the printing process. The lithographic printing plate precursorsuitable for this sort of simplified development, implemented withoutthe post-water washing, necessarily has a photosensitive layer solubleinto a process solution not so strongly alkaline, and the supportthereof necessarily has a hydrophilic surface in view of improvingstaining resistance of the non-image-forming area. However, it waspractically impossible to achieve high printing durability and chemicalresistance with conventional PS plates while satisfying suchrequirements.

Thus, lithographic printing plate precursors comprising a hydrophilicbinder polymer layer containing poly(vinyl phosphonic acid) formed onthe surface of a substrate were proposed to satisfy such requirements(see e.g., Patent Document 5). The precursors were converted into platesby image-exposing them using a UV laser and then developing them in adeveloper at pH 9.8.

Also, lithographic printing plate precursors obtained by hydrophilizinga substrate with poly(vinyl phosphonic acid) were proposed to satisfysuch requirements (see e.g., Patent Document 5). The precursors wereconverted into plates by image-exposing them using a UV laser and thendeveloping them in a developer at pH 9.8.

However, the hydrophilization with poly(vinyl phosphonic acid) or thelike could not achieve enough hydrophilicity to improve stainingresistance, and the resulting plates were insufficient in stainingresistance. As an alternative approach, lithographic printing plateprecursors comprising a layer containing a binder polymer obtained bycopolymerizing a sulfonated monomer and a substrate-adsorbing groupinstead of poly(vinyl phosphonic acid) formed on the surface of asubstrate were proposed (see e.g., Patent Document 6), buthydrophilicity was still insufficient to introduce a hydrophobicpolymerizable group for providing printing durability. Thus, it is verydifficult to improve both printing durability and staining resistance,and any easy-to-handle lithographic printing plate with good stainingresistance and sufficient printing durability has not been known.

One approach for simplifying process steps is a method called on-pressdevelopment by which exposed lithographic printing plate precursors aremounted on a cylinder of a printing press and supplied with a dampeningwater and an ink while the cylinder is rotated to remove non-image areasof the lithographic printing plate precursors. In other words,lithographic printing plate precursors are mounted on a printing pressdirectly after they are image-exposed so that development is completedduring the normal printing process.

Lithographic printing plate precursors suitable for such on-pressdevelopment are required to have not only an image-forming layer solublein dampening waters and ink solvents but also lightroom handlingsuitability for development on a printing press in a lightroom. However,it was practically impossible to sufficiently satisfy such requirementswith conventional PS plates.To satisfy such requirements, lithographic printing plate precursorscomprising a photosensitive layer containing thermoplastic hydrophobicpolymer microparticles dispersed in a hydrophilic binder polymer on ahydrophilic substrate were proposed (see e.g., Patent Document 7). Theywere converted into plates by exposing them to an infrared laser to forman image with the thermoplastic hydrophobic polymer microparticlescoalesced (fused together) by the heat generated by opto-thermalconversion and then mounting them on a cylinder of a printing press andsupplying at least any one of a dampening water and an ink to developthe image on press. The lithographic printing plate precursors are alsosuitable for handling in a lightroom because the image is recorded inthe infrared region.

However, the image formed by coalescing (fusing together) thethermoplastic hydrophobic polymer microparticles is insufficient infastness so that the resulting lithographic printing plates aredisadvantageous in printing durability.

On the other hand, lithographic printing plate precursors comprisingmicrocapsules incorporating a polymerizable compound instead ofthermoplastic microparticles were proposed (see e.g., Patent Document 8,Patent Document 9, Patent Document 10, Patent Document 11, PatentDocument 12, and Patent Document 13). The lithographic printing plateprecursors according to such proposals have the advantage that thepolymer images formed by a reaction of the polymerizable compound aresuperior in fastness to the images formed by coalescence ofmicroparticles.

Further, it has often been proposed to isolate the polymerizablecompound by using microcapsules because it is highly reactive. Moreover,it has been proposed to use thermodegradable polymers for the shells ofthe microcapsules.

However, the conventional lithographic printing plate precursorsdescribed in Patent Document 7, JP-A2000-211262, JP-A2001-277740,JP-A2002-29162, JP-A2002-46361, JP-A2002-137562, and JP-A2002-326470 areinsufficient in the printing durability of the images formed by laserexposure and should be further improved. Thus, substrates having highlyhydrophilic surfaces were used in these easy-to-handle lithographicprinting plate precursors, with the result that image areas were readilyseparated from the substrates with dampening waters during printing andsufficient printing durability could not be attained. If the substratesurfaces are hydrophobic, however, inks also deposit on non-image areasduring printing to cause print staining. Thus, it is very difficult toimprove both printing durability and staining resistance, and anylithographic printing plate precursor suitable for on-press developmentwith good staining resistance and sufficient printing durability has notbeen known.

On the other hand, lithographic printing plate precursors comprising ahydrophilic layer with high adhesion to substrate surfaces to improveboth printing durability and staining resistance have been known. Forexample, Patent Document 14 discloses a substrate for lithographicprinting plates comprising a hydrophilic layer composed of a polymercompound directly chemically bound to the surface of the substrate andhaving a hydrophilic functional group on the substrate. Patent Document15 and Patent Document 16 disclose substrates for lithographic printingplates comprising an aluminum substrate or silicated aluminum substratehaving a hydrophilic surface to which is chemically bound a hydrophilicpolymer having a reactive group capable of being chemically bound to thesubstrate surface directly or through a moiety having a crosslinkingstructure. Patent Document 17 discloses a lithographic printing plateprecursor comprising a photosensitive layer containing a polymerizationinitiator, a polymerizable compound, and a binder polymer soluble orswellable in water or aqueous alkaline solutions on a substrate, whereinthe photosensitive layer or an extra layer contains a copolymercomprising a repeating unitrepeating unit having at least oneethylenically unsaturated bond and a repeating unitrepeating unit havingat least one functional group interacting with the substrate surface.Patent Document 18 discloses a lithographic printing plate precursorcomprising a substrate, a hydrophilic layer formed of a hydrophilicpolymer chemically bound to the surface of the substrate and animage-forming layer in order, wherein the hydrophilic polymer comprisesat least one of a reactive group capable of being directly chemicallybound to the surface of the substrate and a reactive group capable ofbeing chemically bound to the surface of the substrate through acrosslinking structure and a positively and negatively chargedsubstructure.

Recently, there have been demands for not only improving both printingdurability and staining resistance but also improving stainingresistance even when printing takes place at an interval afterpreparation of lithographic printing plates to ensure that thelithographic printing plates can be easily handled during the printingprocess. Thus, not only printing durability and staining resistance butalso staining resistance over time should be improved while striking ahigh level balance among them.

Lithographic printing plate precursors comprising hydrophilic substratesurfaces have also become known, but it is very difficult to satisfy allof printing durability, staining resistance, and developability. This isbecause the materials used for conventional PS plates were stillinsufficient in hydrophilicity so that staining resistance anddevelopability still remained unsatisfactory. Another reason for this isbecause printing durability tends to deteriorate if the hydrophilicityof the materials is increased to improve staining resistance anddevelopability.

For example, Patent Document 19 describes a lithographic printing plateprecursor comprising a substrate having a hydrophilic surface, and animage-recording layer (photosensitive layer) provided on the substrateand containing (A) a polymerization initiator, (B) a polymerizablecompound, and (C) a binder polymer soluble or swellable in water oraqueous alkaline solutions, wherein the photosensitive layer or an extralayer contains a copolymer comprising at least (a1) a repeating unithaving at least one ethylenically unsaturated band and (a2) a repeatingunit having at least one functional group interacting with the surfaceof the substrate. Further, Patent Document 20 describes a substrate forlithographic printing plates treated with an aqueous solvent comprisingPVPA and an amino-containing compound. Patent Document 21 describescopolymers composed of a vinyl phosphonic acid, an alkyl (meth)acrylate,and a tertiary amino-substituted (meth)acrylate. Patent Document 22describes copolymers for lithographic printing plate precursorscomprising a compound having a functional group X (capable ofinteracting with a functional group Y to form a chemical bond anddecrease the contact angle with the substrate surface, such as amino) onthe surface of a substrate.

On the other hand, there have recently been demands for providinglithographic printing plate precursors not only striking a high levelbalance of printing durability with normal inks, staining resistance,and developability but also suitable for use with UV inks because UVinks can be rapidly dried (cured) by UV irradiation, which contributesto high productivity, and they are solvent-free, thereforeenvironmentally-friendly, and further they need not be heated so thatthey widen the range of applications, etc. However, means for improvingprinting durability with UV inks differ from means for improvingprinting durability with normal inks, and accordingly, there have beendemands for a method for improving printing durability with UV inks andprinting durability with normal inks simultaneously. Thus, there havebeen demands for improving not only printing durability with normalinks, staining resistance, and developability but also printingdurability with UV inks and achieving a high level balance among them.

-   [Patent Document 1] U.S. Pat. No. 4,708,925-   [Patent Document 2] JP-A-H8-276558-   [Patent Document 3] U.S. Pat. No. 2,850,445-   [Patent Document 4] JP-B-S44-20189-   [Patent Document 5] JP-A-2009-98590-   [Patent Document 6] JP-A-2009-216926-   [Patent Document 7] JP Resitration No. 2938397-   [Patent Document 8] JP-A-2000-211262-   [Patent Document 9] JP-A-2001-277740-   [Patent Document 10] JP-A-2002-29162-   [Patent Document 11] JP-A-2002-46361-   [Patent Document 12] JP-A-2002-137562-   [Patent Document 13] JP-A-2002-326470-   [Patent Document 14] JP-A-2001-166491-   [Patent Document 15] JP-A-2003-63166-   [Patent Document 16] JP-A-2004-276603-   [Patent Document 17] JP-A-2008-213177-   [Patent Document 18] JP-A-2007-118579-   [Patent Document 19] JP-A-2006-78999-   [Patent Document 20] JP-A-2003-233194-   [Patent Document 21] JP-A-H6-145254-   [Patent Document 22] JP-A-2008-265275

SUMMARY OF THE INVENTION

Under these circumstances, we examined the lithographic printing plateprecursors described in JP-A2001-166491, JP-A2003-63166,JP-A2004-276603, JP-A2008-213177, and JP-A2007-118579 to find that theyhad the disadvantages that staining resistance remained stillinsufficient. Especially, they were found to have the disadvantages thatstaining resistance decreased especially when printing took place at aninterval after lithographic printing plates were prepared.

Thus, a first object to be attained by the present invention is toprovide lithographic printing plate precursors that can be convertedinto lithographic printing plates having excellent printing durability,staining resistance and staining resistance over time and processes forpreparing such lithographic printing plates.

We also examined the lithographic printing plate precursors described inJP-A2006-78999 to find that they still remained unsatisfactory becauseof poor staining resistance due to lack of hydrophilicity. We alsoexamined the lithographic printing plate precursors described inJP-A2003-233194 to find that they still remained unsatisfactory inprinting durability with UV inks. Further, we examined the lithographicprinting plate precursors described in JP-A-H6-145254 to find that theystill remained unsatisfactory because of poor staining resistance due tolack of hydrophilicity. Furthermore, we examined the lithographicprinting plate precursors described in Patent Document 22 to find thatthey still remained unsatisfactory in printing durability with UV inks.Thus, no lithographic printing plate precursor has been known thatachieves a high level balance among printing durability, stainingresistance, and developability as well as printing durability with UVinks.

Thus, a second object to be attained by the present invention is toprovide lithographic printing plate precursors that can be convertedinto lithographic printing plates having excellent developability,staining resistance, printing durability with normal inks and printingdurability with UV inks and processes for preparing such lithographicprinting plates.

Means for Solving the Problems

As a result of careful studies to attain the first object, we found thatprinting durability, staining resistance and staining resistance overtime can be improved simultaneously by using a copolymer comprising arepeating unit having an ethylenically unsaturated group attached to aside chain through a specific bond and a repeating unit having at leastone functional group interacting with the polymerizable surface of thesubstrate.

As a result of careful studies to attain the second object, we foundthat staining resistance and developability can be improved by using acopolymer having a primary or secondary amino-containing side chain inthe photosensitive layer or the primer layer of lithographic printingplate precursors to confer hydrophilicity and printing durability andprinting durability with UV inks can also be improved by controlling thelinking group other than the amino group of the amino-containing sidechain and the substituent.

Thus, we found that the objects described above can be attained by usinglithographic printing plate precursors and processes for preparinglithographic printing plates having the features described below.

The present invention provides the following.[1] A lithographic printing plate precursor comprising:a substrate;a photosensitive layer provided on the substrate; andan extra layer optionally provided between the substrate and thephotosensitive layer;wherein the photosensitive layer or the extra layer adjacent to thesubstrate contains (A) a copolymer; andwherein the copolymer (A) comprises:(a1) a repeating unit having a structure represented by formula (a1-1)below in a side chain, and(a2) a repeating unit having at least one of the structures representedby formulae (a2-1), (a2-1), (a2-3), (a2-4), (a2-5) and (a2-6) below in aside chain.

In formula (a1-1), L¹ represents a single bond, a divalent aromaticgroup containing 6 to 14 carbon atoms, —C(═O)—O—, or —C(═O)—NR²—(wherein R² represents a hydrogen atom, alkyl or aryl). Z¹ represents adivalent linking group selected from the group consisting of a divalentaliphatic group containing 1 to 14 carbon atoms, a divalent aromaticgroup containing 6 to 14 carbon atoms, —NH—, —O—, —S— and a combinationthereof, provided that both ends are not —NH—, —O— or —S—, and when L¹is a divalent aromatic group containing 6 to 14 carbon atoms, Z¹ is nota divalent aromatic group containing 6 to 14 carbon atoms, and thedivalent aliphatic group, divalent aromatic group and —NH— may have asubstituent instead of a hydrogen atom. R¹ represents a hydrogen atom,alkyl, aryl, heterocyclyl, sulfo, alkylsulfonyl and arylsulfonyl. R²¹,R²² and R²³ each independently represent a hydrogen atom, halogen atomor C1-8 alkyl. The asterisk (*) indicates the point of attachment to themain chain of the copolymer.

In formulae (a2-1) to (a2-6), M¹ to M⁸ each independently represent ahydrogen atom, a metal atom contained in an alkali metal or an alkalineearth metal or ammonium. R⁴¹ to R⁴⁶ each independently represent ahydrogen atom or alkyl. Y²¹ to Y^(Z6) represent a single bond, or adivalent linking group selected from the group consisting of —CO—, —O—,—NH—, a divalent aliphatic group, a divalent aromatic group and acombination thereof. The asterisk (*) indicates the point of attachmentto the main chain of the polymer compound. [2] The lithographic printingplate precursor according to [1], wherein Z¹ in formula (a1-1) above isa group selected from group A below or a combination thereof.

(Group A)

In group A, R⁵² to R⁵⁵ each independently represent a hydrogen atom,halogen atom, hydroxyl, alkoxy, alkyl, aryl or cyano. R⁵⁶ eachindependently represents a halogen atom, hydroxyl, alkoxy, alkyl, arylor cyano, n each independently represents an integer of 0 to 4, and mrepresents an integer of 0 to 2. If a plurality of R⁵⁶ groups exist,they may be identical or different.

[3] The lithographic printing plate precursor according to [1] or [2],wherein the photosensitive layer contains (B) a polymerizationinitiator, (C) a polymerizable compound, (D) a binder and (E) a dye.[4] The lithographic printing plate precursor according to any one of[1] to [3], wherein the copolymer (A) is contained in the extra layer.[5] The lithographic printing plate precursor according to any one of[1] to [4], wherein Z¹ in formula (a1-1) above is a group selected fromgroup B below or a combination thereof.

(Group B)

In group B, R⁵¹ to R⁵³ each independently represent a hydrogen atom,halogen atom, hydroxyl, alkoxy, alkyl, aryl or cyano. [6] Thelithographic printing plate precursor according to any one of [1] to[5], wherein Z¹ in formula (a1-1) above is C1-14 alkylene, or a divalentlinking group having a linking chain length of 1 to 14 atoms andcomposed of two or more alkylenes linked through an oxygen atom linkinggroup (wherein the alkylenes may each independently be substituted).

[7] The lithographic printing plate precursor according to any one of[1] to [6], wherein the repeating unit (a2) in the copolymer (A) has aside chain of a structure represented by formula (a2-1) above or formula(a2-2).[8] The lithographic printing plate precursor according to any one of[1] to [7], wherein the copolymer (A) further comprises (a3) a repeatingunit having a hydrophilic group in a side chain.[9] The lithographic printing plate precursor according to [8], whereinthe hydrophilic group contained in the repeating unit (a3) having ahydrophilic group in a side chain is a group having a zwitterionicstructure represented by formula (a3-1) or formula (a3-2) below:

In formula (a3-1), R³¹ and R³² each independently represent a hydrogenatom, alkyl, alkenyl, alkynyl, aryl, or heterocyclyl, or R³¹ and R³² maybe joined together to form a ring structure, L³¹ represents a linkinggroup, and A- represents an anion-containing structure. Y³ represents asingle bond, or a divalent linking group selected from the groupconsisting of —CO—, —O—, —NH—, a divalent aliphatic group, a divalentaromatic group and a combination thereof. The asterisk (*) indicates thepoint of attachment to the main chain of the copolymer.

In formula (a3-2) above, L³² represents a linking group, and E⁺represents a cation-containing structure. Y⁴ represents a single bond,or a divalent linking group selected from the group consisting of —CO—,—O—, —NH—, a divalent aliphatic group, a divalent aromatic group and acombination thereof. The asterisk (*) indicates the point of attachmentto the main chain of the copolymer.[10] The lithographic printing plate precursor according to [9], whereinthe group having a zwitterionic structure is represented by formula(a3-1) above.[11] The lithographic printing plate precursor according to [9] or [10],wherein A- in formula (a3-1) above is sulfonate.[12] A process for preparing a lithographic printing plate, comprising:image-exposing a lithographic printing plate precursor according to anyone of [1] to [11]; anddeveloping the exposed lithographic printing plate precursor in thepresence of a developer having a pH of 2 to 14 to remove thephotosensitive layer in unexposed areas.[13] The process for preparing a lithographic printing plate accordingto [12], comprising forming a protective layer on the surface of thephotosensitive layer opposite to the substrate;wherein the developing comprises removing the photosensitive layer inunexposed areas and the protective layer simultaneously in the presenceof the developer further containing a surfactant without includingwater-washin.[14] The process for preparing a lithographic printing plate accordingto [12] or [13], comprising controlling the pH of the developer at 2.0to 10.0.[15] A process for preparing a lithographic printing plate, comprising:image-exposing a lithographic printing plate precursor according to anyone of [1] to [11]; and supplying a printing ink and a dampeningsolution on a printing press to remove the photosensitive layer inunexposed areas.[16] A copolymer comprising:(a1) a repeating unit having a structure represented by formula (a1-1)below in a side chain;(a2) a repeating unit having at least one of the structures representedby formulae (a2-1), (a2-1), (a2-3), (a2-4), (a2-5) and (a2-6) in a sidechain; and(a3′) a repeating unit having a zwitterionic structure represented byformula (a3-1) or (a3-2) below in a side chain.

In formula (a1-1), L¹ represents a single bond, a divalent aromaticgroup containing 6 to 14 carbon atoms, —C(═O)—O—, or —C(═O)—NR²—(wherein R² represents a hydrogen atom, alkyl or aryl). Z¹ represents adivalent linking group selected from the group consisting of a divalentaliphatic group containing 1 to 14 carbon atoms, a divalent aromaticgroup containing 6 to 14 carbon atoms, —NH—, —O—, —S— and a combinationthereof, provided that both ends are not —NH—, —O— or —S—, and when L¹is a divalent aromatic group containing 6 to 14 carbon atoms, Z¹ is nota divalent aromatic group containing 6 to 14 carbon atoms, and thedivalent aliphatic group, divalent aromatic group and —NH— may have asubstituent instead of a hydrogen atom. R¹ represents a hydrogen atom,alkyl, aryl, heterocyclyl, sulfo, alkylsulfonyl and arylsulfonyl. R²¹,R²² and R²³ each independently represent a hydrogen atom, halogen atomor C1-8 alkyl. The asterisk (*) indicates the point of attachment to themain chain of the copolymer.

wherein M¹ to M⁸ each independently represent a hydrogen atom, a metalatom contained in an alkali metal or an alkaline earth metal orammonium. R⁴¹ to R⁴⁶ each independently represent a hydrogen atom oralkyl. Y²¹ to Y²⁶ represent a single bond, or a divalent linking groupselected from the group consisting of —CO—, —O—, —NH—, a divalentaliphatic group, a divalent aromatic group and a combination thereof.The asterisk (*) indicates the point of attachment to the main chain ofthe polymer compound.

In formula (a3-1), R³¹ and R³² each independently represent a hydrogenatom, alkyl, alkenyl, alkynyl, aryl, or heterocyclyl, or R³¹ and R³² maybe joined together to form a ring structure, L³¹ represents a linkinggroup, and A- represents an anion-containing structure. Y³ represents asingle bond, or a divalent linking group selected from the groupconsisting of —CO—, —O—, —NH—, a divalent aliphatic group, a divalentaromatic group and a combination thereof. The asterisk (*) indicates thepoint of attachment to the main chain of the polymer compound.

In formula (a3-2) above, L³² represents a linking group, and E⁺represents a cation-containing structure. Y⁴ represents a single bond,or a divalent linking group selected from the group consisting of —CO—,—O—, —NH—, a divalent aliphatic group, a divalent aromatic group and acombination thereof. The asterisk (*) indicates the point of attachmentto the main chain of the polymer compound.[17] The copolymer according to [16], wherein Z¹ in the repeating unithaving a structure represented by formula (a1) above is selected fromgroup A below:

In group A, R⁵¹ to R⁵⁵ each independently represent a hydrogen atom,halogen atom, hydroxyl, alkoxy, alkyl, aryl or cyano. R⁵⁶ eachindependently represents a halogen atom, hydroxyl, alkoxy, alkyl, arylor cyano, n each independently represents an integer of 0 to 4, and mrepresents an integer of 0 to 2. If a plurality of R⁵⁶ groups exist,they may be identical or different.

The copolymer according to [16] or [17], wherein Z¹ in the repeatingunit having a structure represented by formula (a1) above is selectedfrom group B below:

(Group B)

In group B, R⁵¹ to R⁵³ each independently represent a hydrogen atom,halogen atom, hydroxyl, alkoxy, alkyl, aryl or cyano.[19] The copolymer according to any one of [16] to [18], wherein therepeating unit (a2) has a side chain of a structure represented byformula (a2-1) above or formula (a2-2).[20] The copolymer according to any one of [16] to [19], wherein theside chain having a zwitterionic structure in the repeating unit (a3′)is a structure represented by formula (a3-1) above.[21] The copolymer according to any one of [16] to [20], wherein A- informula (a3-1) above is sulfonate.[22] A process for preparing the copolymer according to any one of [16]to [21], comprising introducing the repeating unit (a1) having astructure represented by formula (a1-1) above in a side chain byreacting a polymer comprising:(a0) a repeating unit having a structure represented by formula (a1-0)below in a side chain;(a2) the repeating unit having a structures represented by any one offormulae (a2-1), (a2-1), (a2-3), (a2-4), (a2-5) and (a2-6) above in aside chain; and(a3′) the repeating unit having a zwitterionic structure represented byformula (a3-1) or (a3-2) above in a side chain;with a compound represented by formula (b-1) or (b-2) below.

In formula (a1-0), L¹⁰¹ represents a single bond, a divalent aromaticgroup containing 6 to 14 carbon atoms, —C(═O)—O—, or —C(═O)—NR¹⁰²—(wherein R¹⁰² represents a hydrogen atom, alkyl or aryl). Z¹⁰¹represents a divalent linking group selected from the group consistingof a divalent aliphatic group containing 1 to 14 carbon atoms, adivalent aromatic group containing 6 to 14 carbon atoms, —NH—, —O—, —S—and a combination thereof, provided that both ends are not —NH—, —O— or—S—, and when L¹ is a divalent aromatic group containing 6 to 14 carbonatoms, Z¹ is not a divalent aromatic group containing 6 to 14 carbonatoms, and the divalent aliphatic group, divalent aromatic group and—NH— may have a substituent instead of a hydrogen atom. R¹⁰¹ representsa hydrogen atom, alkyl, aryl, heterocyclyl, sulfo, alkylsulfonyl andarylsulfonyl. The asterisk (*) indicates the point of attachment to themain chain of the copolymer.

In formulae (b-1) and (b-2), R¹¹¹ represents a halogen atom, anoptionally substituted C1-8 alkoxy, or —OSOR¹¹². R¹¹² represents anoptionally substituted C1-8 alkyl. R¹²¹ to R¹²⁹ each independentlyrepresent a hydrogen atom, halogen atom or C1-8 alkyl.[23] A lithographic printing plate precursor comprising:a substrate;a photosensitive layer provided on the substrate and containing at least(B) a polymerization initiator, (C) a polymerizable compound and (D) abinder; and an extra layer optionally provided between the substrate andthe photosensitive layer;wherein the photosensitive layer or the extra layer adjacent to thesubstrate contains (A) a copolymer different from (D) the binder andcontaining a compound comprising (a0) a repeating unit having astructure represented by formula (a1-0) below in a side chain.

In formula (a1-0), L¹ represents a divalent covalent linking group,excluding alkylene. Z¹ represents a covalent linking group selected fromthe group consisting of alkylene, arylene, —O—, —S— and a combinationthereof, provided that both ends are not —O— or —S—, and when L¹ isarylene, Z¹ is not arylene. X¹ represents a hydrogen atom or anelectron-releasing group having a Hammett substituent constant op valueof 0.2 or less. The asterisk (*) indicates the point of attachment tothe main chain of the copolymer.[24] The lithographic printing plate precursor according to [23],wherein Z¹ in formula (a1-0) above represents a linking group selectedfrom the group consisting of alkylene, arylene, —O— and a combinationthereof, provided that —O—is not terminal.[25] The lithographic printing plate precursor according to [23] or[24], wherein X¹ in formula (a1-0) above represents a hydrogen atom,alkyl, aryl or heterocyclyl.[26] The lithographic printing plate precursor according to any one of[23] to [25], wherein the copolymer (A) comprises (a2) a repeating unithaving at least one functional group interacting with the substratesurface.[27] The lithographic printing plate precursor according to any one of[23] to [26], wherein the copolymer (A) comprises (a1) a repeating unithaving a structure represented by formula (a1-1) below in a side chain.

In formula (a1-1), L² represents a divalent covalent linking group,excluding alkylene. Z² represents a covalent linking group selected fromthe group consisting of alkylene, arylene, —O—, —S— and a combinationthereof, provided that —O— and —S— are not terminal, and when L¹ isarylene. Z¹ is not arylene. X² represents a hydrogen atom or anelectron-releasing group having a Hammett substituent constant op valueof 0.2 or less. R represents a substituent. The asterisk (*) indicatesthe point of attachment to the main chain of the copolymer.[28] The lithographic printing plate precursor according to [27],wherein R in formula (a1-1) above is a radically polymerizable reactivegroup.[29] The lithographic printing plate precursor according to any one of[26] to [28], wherein the functional group interacting with thesubstrate surface contained in (a2) the repeating unit having at leastone functional group interacting with the substrate surface is selectedfrom a phosphoric acid ester or a salt thereof, or a phosphonic acid ora salt thereof.[30] The lithographic printing plate precursor according to any one of[23] to [29], wherein the extra layer is a primer layer provided betweenthe substrate and the photosensitive layer.[31] The lithographic printing plate precursor according to any one of[23] to [30], wherein the copolymer (A) comprises (a3) a repeating unithaving a hydrophilic group in a side chain.[32] The lithographic printing plate precursor according to [31],wherein the hydrophilic group contained in (a3) the repeating unithaving a hydrophilic group in a side chain is selected from azwitterionic structure represented by formula (a3-1) or formula (a3-2)below.

In formula (a3-1), R³¹ and R³² each independently represent a hydrogenatom, alkyl, alkenyl, alkynyl, aryl or heterocyclyl, or R³¹ and R³² maybe joined together to form a ring structure, and L³¹ represents adivalent linking group. A⁻ represents an anion-containing structure. Y³represents a single bond, or a divalent linking group selected from thegroup consisting of —CO—, —O—, —NH—, a divalent aliphatic group, adivalent aromatic group and a combination thereof. The asterisk (*)indicates the point of attachment to the main chain of the copolymer.

In formula (a3-2), L³² represents a divalent linking group, andrepresents a cation-containing structure. Y⁴ represents a single bond,or a divalent linking group selected from the group consisting of —CO—,—O—, —NH—, a divalent aliphatic group, a divalent aromatic group and acombination thereof. The asterisk (*) indicates the point of attachmentto the main chain of the copolymer.[33] The lithographic printing plate precursor according to any one of[27] to [32], wherein (a1) the repeating unit having a structurerepresented by formula (a1-1) in a side chain in the copolymer (A) wasobtained by a substitution reaction of the hydrogen atom attached to thenitrogen atom attached to X¹ and Z¹ of (a0) the repeating unit having astructure represented by formula (a1-0) in a side chain.[34] The lithographic printing plate precursor according to any one of[23] to [33], comprising a protective layer on the surface of thephotosensitive layer opposite to the substrate.[35] A process for preparing a lithographic printing plate, comprising:image-exposing a lithographic printing plate precursor according to anyone of [23] to [33]; and developing the exposed lithographic printingplate precursor in a developer containing a surfactant;wherein the developing comprises removing unexposed areas of thephotosensitive layer and the protective layer simultaneously in thepresence of the developer.[36] The process for preparing a lithographic printing plate accordingto [35], wherein the developing comprises removing unexposed areas ofthe photosensitive layer and the protective layer simultaneously in thepresence of the developer without including water-washing.[37] The process for preparing a lithographic printing plate accordingto [35] or [36], wherein the exposing comprises exposure using a laserlight having a wavelength of 350 nm to 450 nm.[38] The process for preparing a lithographic printing plate accordingto any one of [35] to [37], comprising controlling the pH of thedeveloper at 2.0 to 10.0.[39] The process for preparing a lithographic printing plate accordingto any one of [35] to [38], wherein the developer contains carbonateions and bicarbonate ions.

Advantages of the Invention

According to a first feature of the present invention, lithographicprinting plates having excellent printing durability, stainingresistance and staining resistance over time can be provided as well asprocesses for preparing such lithographic printing plates. According toa second feature of the present invention, lithographic printing plateprecursors that can be converted into lithographic printing plateshaving excellent developability, handling properties, printingdurability with normal inks and printing durability with UV inks can beprovided as well as processes for preparing such lithographic printingplates.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory drawing illustrating an exemplary configurationof an automatic processor; and

FIG. 2 is an explanatory drawing illustrating another exemplaryconfiguration of the automatic processor.

THE BEST MODES FOR CARRYING OUT THE INVENTION

The present invention will be explained in detail below. The descriptionof essential features below may be sometimes based on representativeembodiments of the present invention, but the present invention is notlimited to such embodiments. As used herein, the numerical rangesexpressed with “to” are used to mean the ranges including the valuesindicated before and after “to” as lower and upper limits.

As used herein, any reference to a group in a compound represented by aformula without indicating that the group is substituted orunsubstituted includes the group not only unsubstituted but alsosubstituted if the group may be further substituted, unless otherwisespecified. For example, the reference in a formula that “R representsalkyl, aryl or heterocyclyl” means that “R represents unsubstitutedalkyl, substituted alkyl, unsubstituted aryl, substituted aryl,unsubstituted heterocyclyl or substituted heterocyclyl”. As used herein,“(meth)acrylamide” refers to the concept including both methacrylamideand acrylamide.As used herein, the term “printing durability” refers to printingdurability with normal inks, unless otherwise specified.

First Embodiment Lithographic Printing Plate Precursor

A lithographic printing plate precursor according to a first embodimentof the present invention is explained in detail below.The lithographic printing plate precursor of the present inventioncomprises a substrate, a photosensitive layer provided on the substrate,and an extra layer optionally provided between the substrate and thephotosensitive layer; wherein the photosensitive layer or the extralayer adjacent to the substrate contains (A) a copolymer, and whereinthe copolymer (A) comprises (a1) a repeating unit having a structurerepresented by formula (a1-1) below in a side chain, and (a2) arepeating unit having at least one of the structures represented byformulae (a2-1) (a2-1) (a2-3), (a2-4), (a2-5) and (a2-6) below in a sidechain.

In formula (a1-1), L¹ represents a single bond, a divalent aromaticgroup containing 6 to 14 carbon atoms, —C(═O)—O—, or —C(═O)—NR²—(wherein R² represents a hydrogen atom, alkyl or aryl). Z¹ represents adivalent linking group selected from the group consisting of a divalentaliphatic group containing 1 to 14 carbon atoms, a divalent aromaticgroup containing 6 to 14 carbon atoms, —NH—, —O—, —S— and a combinationthereof, provided that both ends are not —NH—, —O— or —S—, and when L¹is a divalent aromatic group containing 6 to 14 carbon atoms, Z¹ is nota divalent aromatic group containing 6 to 14 carbon atoms, and thedivalent aliphatic group, divalent aromatic group and —NH— may have asubstituent instead of a hydrogen atom. R represents a hydrogen atom,alkyl, aryl, heterocyclyl, sulfo, alkylsulfonyl and arylsulfonyl. R²¹,R²² and R²³ each independently represent a hydrogen atom, halogen atomor C1-8 alkyl. The asterisk (*) indicates the point of attachment to themain chain of the copolymer.

In formulae (a2-1) to (a2-6), M¹ to M⁸ each independently represent ahydrogen atom, a metal atom contained in an alkali metal or an alkalineearth metal or ammonium. R⁴¹ to R⁴⁶ each independently represent ahydrogen atom or alkyl. Y²¹ to Y²⁶ represent a single bond, or adivalent linking group selected from the group consisting of —CO—, —O—,—NH—, a divalent aliphatic group, a divalent aromatic group and acombination thereof. The asterisk (*) indicates the point of attachmentto the main chain of the polymer compound. The copolymer (A) comprising(a1) a repeating unit having a structure represented by formula (a1-1)below in a side chain, and (a2) a repeating unit having at least one ofthe structures represented by formulae (a2-1), (a2-1), (a2-3), (a2-4),(a2-5) and (a2-6) below in a side chain is hereinafter also referred toas a specific polymer compound.

Without being bound to any theory, it is assumed that the advantages ofthe present invention can be achieved by the lithographic printing plateprecursor of the present invention containing the copolymer (A) in thephotosensitive layer or the extra layer (preferably a primer layerbetween the substrate and the photosensitive layer) for the followingreasons. Polymers having a structure represented by (a1-1) above in aside chain exhibit strong and high adhesion by radical polymerization ofthe compound in the photosensitive layer and a (meth)acrylamide group.Further, non-image areas (unexposed areas) can be prevented fromadhering to the photosensitive layer after development and can beprovided with a substrate surface having unprecedentedly highhydrophilicity because of the hydrophilicity of the (meth)acrylamidegroup and the presence of a spacer selected from a specific grouphindering electrostatic interaction with the photosensitive layerespecially in the point of attachment of polymerizable groups to themain chain where electrostatic interaction with the photosensitive layerotherwise would be liable to occur. This may contribute to theachievement of the objects of the present invention, i.e., lithographicprinting plate precursors that can be converted into lithographicprinting plates having very excellent staining resistance and stabilityover time and excellent printing durability (more preferably, alsohaving excellent developability) can be provided as well as processesfor preparing such lithographic printing plates.

Moreover, the copolymer (A) having a structure represented by formula(a1-1) can be synthesized by using a polymer having an amine structurein a side chain as exemplified by formula (a1-0) as a precursor. Aminecompounds typically have high nucleophilic reactivity, which allows adesired reaction to be performed even in protic solvents. Thus,polymerizable groups can be introduced into polymers in protic solventsby taking advantage of the reactivity of amine structures even if thepolymers have low solubility in aprotic solvents and high solubility inprotic solvents such as alcohols, water and the like, with the resultthat very highly hydrophilic polymers having a radically polymerizablegroup can be synthesized.

Preferably, the lithographic printing plate precursor of the presentinvention can be directly converted into a plate using various lasersfrom digital signals of computers or the like, i.e., it is applicable toso-called computer-to-plate. Preferably, it can also be developed inaqueous solutions at pH 2.0 to 10.0 or less or on a printing press.

Preferred aspects of the lithographic printing plate precursor of thepresent invention are explained in detail below.

The lithographic printing plate precursor of the present inventioncomprises a substrate and a photosensitive layer provided on thesubstrate.

Further, the lithographic printing plate precursor of the presentinvention may optionally comprise an extra layer between the substrateand the photosensitive layer. The lithographic printing plate precursorof the present invention preferably comprises a primer layer as theextra layer.Further, the lithographic printing plate precursor of the presentinvention preferably comprises a protective layer on the surface of thephotosensitive layer opposite to the substrate.Further, the lithographic printing plate precursor of the presentinvention may comprise a back coating layer on the bottom of thesubstrate as appropriate.The photosensitive layer, extra layer, protective layer, and backcoating layer constituting the lithographic printing plate precursor ofthe present invention are explained in order below, and processes forforming the lithographic printing plate precursor of the presentinvention are also explained.

<Photosensitive Layer>

The photosensitive layer of the lithographic printing plate precursor ofthe present invention preferably contains (B) a polymerizationinitiator, (C) a polymerizable compound, (D) a binder and (E) a dye.Further, the lithographic printing plate precursor of the presentinvention is characterized in that the photosensitive layer or the extralayer contains (A) a copolymer and that the copolymer (A) comprises (a1)a repeating unit having a structure represented by formula (a1-1) in aside chain, and (a2) a repeating unit having at least one of thestructures represented by formulae (a2-1), (a2-1), (a2-3), (a2-4),(a2-5) and (a2-6) in a side chain. Thus, the photosensitive layer maycontain the copolymer (A). When the primer layer described below isprovided as the extra layer between the substrate and the photosensitivelayer, the photosensitive layer may not contain the copolymer (A), butthe primer layer may contain the copolymer (A). However, the primerlayer preferably contains the copolymer (A) in the lithographic printingplate precursor of the present invention.It should be noted that the copolymer (A) differs from the binder (D).Further, the photosensitive layer may further contain other componentsas appropriate.

The components of the photosensitive layer are explained in detailbelow.

(A) Copolymer

In the lithographic printing plate precursor of the present invention,the photosensitive layer adjacent to the substrate may contain (A) acopolymer comprising a (a1) a repeating unit having a structurerepresented by formula (a1-1) below in a side chain and (a2) a repeatingunit having at least one of the structures represented by formulae(a2-1) to (a2-6) in a side chain. Although the primer layer preferablycontains the copolymer (A) in the lithographic printing plate precursorof the present invention, the copolymer (A) (specific polymer compound)is described in detail below in the photosensitive layer for sake ofexplanation.

(a1) Repeating unit having a structure represented by formula (a1-1):

First, a repeating unit having a structure represented by formula (a1-1)above is explained.

In formula (a1-1), L¹ represents a single bond, a divalent aromaticgroup containing 6 to 14 carbon atoms, —C(═O)—O—, or —C(═O)—NR²—(wherein R² represents a hydrogen atom, alkyl or aryl).

Specific examples of the L¹ group defined above are shown below. In theexamples below, each group is attached to the main chain at the leftend.

L2: —CO—O— a divalent aromatic group-L4: —CO—NH— a divalent aromatic group-

L5: —CO—NH— L6: —CO—O—

The divalent aromatic group refers to a divalent monocyclic orpolycyclic aromatic hydrocarbon group. Specific examples of the divalentaromatic group include, for example, 1,2-phenylene, 1,3-phenylene,1,4-phenylene, biphenyl-4,4′-diyl, diphenylmethane-4,4′-diyl,3,3′-dimethylbiphenyl-4,4′-diyl, 1,2-naphthalene, 1,5-naphthalene,2,6-naphthalene and the like. Examples of substituents on the divalentaromatic group include halogen atoms (F, Cl, Br, I), hydroxy, carboxy,amino, cyano, aryl, alkoxy, aryloxy, monoalkylamino, dialkylamino,arylamino and diarylamino, as well as alkyl.

L¹ is preferably a single bond, a divalent aromatic group, or L5 or L6shown above. To improve staining resistance, L¹ is preferably L5 or L6defined above, more preferably L5.

In formula (a1-1) above, the divalent linking group represented by Z¹refers to a divalent linking group selected from the group consisting ofa divalent aliphatic group containing 1 to 14 carbon atoms, a divalentaromatic group containing 6 to 14 carbon atoms, —NH—, —O—, —S— and acombination thereof, provided that both ends are not —NH—, —O— or —S—,and when L¹ is a divalent aromatic group containing 6 to 14 carbonatoms, Z¹ is not a divalent aromatic group containing 6 to 14 carbonatoms, and the divalent aliphatic group, divalent aromatic group and—NH— may have a substituent instead of a hydrogen atom.

The divalent aliphatic group here refers to alkylene, substitutedalkylene, alkenylene, substituted alkenylene, alkynylene, substitutedalkynylene or polyalkyleneoxy. Among others, alkylene, substitutedalkylene, alkenylene, and substituted alkenylene are preferred, morepreferably alkylene and substituted alkylene.

The divalent aliphatic group preferably has a chain structure to a ringstructure, more preferably has a straight-chain structure to a branchedchain structure. The divalent aliphatic group preferably contains 1 to20, more preferably 1 to 15, even more preferably 1 to 12, especiallypreferably 1 to 10 carbon atoms.

Examples of substituents on the divalent aliphatic group include halogenatoms (F, Cl, Br, I), hydroxy, carboxy, amino, cyano, aryl, alkoxy,aryloxy, monoalkylamino, dialkylamino, arylamino and diarylamino and thelike.

The divalent aromatic group refers to a divalent monocyclic orpolycyclic aromatic hydrocarbon group. Specific examples of the divalentaromatic group include, for example, 1,2-phenylene, 1,3-phenylene,1,4-phenylene, biphenyl-4,4′-diyl, diphenylmethane-4,4′-diyl,3,3′-dimethylbiphenyl-4,4′-diyl, 1,2-naphthalene, 1,5-naphthalene,2,6-naphthalene and the like.

Examples of substituents on the divalent aromatic group include theexamples of substituents on the divalent aliphatic group listed above,as well as alkyl.

In the lithographic printing plate precursor of the present invention,the divalent linking group represented by Z¹ in formula (a1-1) above ispreferably a group selected from group A or a combination thereof.

(Group A)

In group A, R⁵¹ to R⁵⁵ each independently represent a hydrogen atom,halogen atom, hydroxyl, alkoxy, alkyl, aryl or cyano. R⁵⁶ eachindependently represents a halogen atom, hydroxyl, alkoxy, alkyl, arylor cyano, n represents an integer of 0 to 4, and m represents an integerof 0 to 2. If a plurality of R⁵⁶ groups exist, they may be identical ordifferent.

Especially when the copolymer (A) is contained in the primer layer, R⁵¹to R⁵⁵ preferably represent a hydrogen atom, halogen atom (—F, —Br, —Cl,—I), hydroxyl, alkoxy or alkyl, more preferably a hydrogen atom, halogenatom (—F, —Br, —Cl, —I), hydroxyl or C1-8 alkyl, especially preferably ahydrogen atom, to improve interaction with the photosensitive layer.Preferably, R⁵⁶ represents a halogen atom (—F, —Br, —Cl, —I) hydroxyl,alkoxy or alkyl, more preferably a halogen atom (—F, —Br, —Cl, —I),hydroxyl or C1-8 alkyl.Preferably, n is an integer of 0 to 3, more preferably 0. Preferably, mis 0 or 1, more preferably 0.

A highly hydrophilic substrate surface can be provided by using acombination of divalent linking groups selected from group A because theabsence of carbonyl in the so-called spacer Z¹ in formula (a1-1) abovehinders interaction with the photosensitive layer, thereby preventingdevelopment failure and improving staining resistance.

More preferably, Z¹ in formula (a1-1) above is a group selected fromgroup B below or a combination thereof to improve the hydrophilicity ofthe spacer itself.

(Group B)

In group B, R⁵¹ to R⁵³ each independently represent a hydrogen atom,halogen atom, hydroxyl, alkoxy, alkyl, aryl or cyano. In group B above,R⁵¹ to R⁵³ have the same meanings as defined for R⁵¹ to R⁵³ in group A,and also cover similar preferred ranges.

For similar reasons, Z¹ in formula (a1-1) above is especially preferablya group selected from group C or a combination thereof.

(Group C)

In group C, R⁵² and R⁵³ each independently represent a hydrogen atom,halogen atom, hydroxyl, alkoxy, alkyl, aryl or cyano.In group B above, R⁵² and R⁵³ have the same meanings as defined for R⁵²and R⁵³ in group A, and also cover similar preferred ranges.In formula (a1-1) above, the structure represented by Z¹ is preferablymethylene, ethylene, propylene, butylene, pentylene, hexylene,heptylene, octylene, cyclohexane-1,4-diyl, 1,2-phenylene, 1,3-phenylene,1,4-phenylene, 1,2-naphthalene, 1,5-naphthalene and a linking groupcomposed of two or more of these divalent linking groups linked through—O— or —S—, more preferably methylene, ethylene, propylene, butylene,pentylene, hexylene, 1,3-phenylene, 1,4-phenylene, 1,5-naphthalene and alinking group composed of two or more of these divalent linking groupslinked through —O—.Specifically, the following structures are included, but the presentinvention is not limited to these examples. Methylene, ethylene,propylene, butylene, pentylene, 1,4-phenylene, —C₂H₄—O—C₂H₄—,—C₂H₄—O—C₂H₄—O—C₂H₄—, —C₂H₄—O—C₂H₄—O—C₂H₄—O—C₂H₄—,—C₃H₆—O—C₂H₄—O—C₂H₄—O—C₃H₆—, —CH₂—C≡C—CH₂—,—CH₂-cyclohexane-1,4-diyl-CH₂—,1,4-phenylene-O-1,4-phenylene-O-1,4-phenylene-,—C₂H₄—O-1,4-phenylene-O-1,4-phenylene-O—C₂H₄—, —CH₂-1,4-phenylene-CH₂—,—C₂H₄—S—C₂H₄—, —C₂H₄—NH—C₂H₄—NH—C₂H₄—, —CH(OH)—CH(OH)—.Moreover, the hydrogen atoms in these groups may be replaced bysubstituents.Among them, the structure represented by Z¹ in formula (a1-1) above ispreferably C1-14 alkylene, or a divalent linking group having a linkingchain length of 1 to 14 atoms and contains two or more alkylenes linkedthrough an oxygen atom linking group wherein the alkylenes may eachindependently have a substituent. The divalent linking group having alinking chain length of 1 to 14 atoms and containing two or morealkylenes linked through an oxygen atom linking group is preferably anethylene oxide chain, a propylene oxide chain, and a combinationthereof.

In formula (a1-1) above, R¹ represents a hydrogen atom, or an optionallysubstituted alkyl, aryl, heterocyclyl, sulfo, alkylsulfonyl andarylsulfonyl.

The alkyl refers to a straight-chain, branched chain, or cyclicsubstituted or unsubstituted alkyl. Examples include alkyl (preferablyC1-30 alkyl, e.g., methyl, ethyl, n-propyl, isopropyl, t-butyl, n-octyl,eicosyl, 2-chloroethyl, 2-cyanoethyl, 2-ethylhexyl), cycloalkyl(preferably a substituted or unsubstituted C3-30 cycloalkyl, e.g.,cyclohexyl, cyclopentyl, 4-n-dodecylcyclohexyl), bicycloalkyl(preferably a substituted or unsubstituted C5-30 bicycloalkyl, i.e., amonovalent group obtained by removing one hydrogen atom from a C5-30bicycloalkane; e.g., bicyclo[1,2,2]heptane-2-yl,bicyclo[2,2,2]octane-3-yl), as well as tricyclo structure containingmore ring structures and the like. It should be noted that the alkyls inthe substituents explained below (e.g., alkyl in alkylthio) also referto such a category of alkyls. The aryl preferably refers to asubstituted or unsubstituted C6-30 aryl, e.g., phenyl, p-tolyl,nephthyl, m-chlorophenyl, o-hexadecanoylaminophenyl.

The heterocyclyl is preferably a monovalent group obtained by removingone hydrogen atom from a substituted or unsubstituted 5- or 6-memberedaromatic or non-aromatic heterocyclic compound, even more preferably a5- or 6-membered aromatic heterocyclyl containing 3 to 30 carbon atoms.For example, 2-furyl, 2-thienyl, 2-pyrimidinyl, and 2-benzothiazolyl arepreferred.The sulfo, alkylsulfonyl and arylsulfonyl are preferably a substitutedor unsubstituted C1-30 alkylsulfonyl, and a substituted or unsubstitutedC6-30 arylsulfonyl, e.g., methylsulfonyl, ethylsulfonyl, phenylsulfonyl,p-methylphenylsulfonyl.

In formula (a1-1) above, R¹ is preferably a hydrogen atom, an optionallysubstituted alkyl, aryl and heterocyclyl, more preferably a hydrogenatom, an optionally substituted alkyl and aryl, especially preferably ahydrogen atom or methyl, more especially preferably a hydrogen atom.

In formula (a1-1) above, R²¹, R²² and R²³ each independently represent ahydrogen atom, halogen atom or C1-8 alkyl. Preferably, R²¹, R²² and R²³each independently represent a hydrogen atom, C1-6 alkyl or halogen atom(—F, —Br, —Cl, —I). More preferably, at least two of R²¹, R²² and R²³are a hydrogen atom, and the remaining one is a hydrogen atom or C1-6alkyl. Especially preferably, at least two of R²¹, R²² and R²³ are ahydrogen atom, and the remaining one is a hydrogen atom or methyl.

Specific examples of structures represented by formula (a1-1) above inthe present invention are shown below, but the present invention is notlimited to these examples.

The repeating unit (a1) having a structure represented by formula (a1-1)in a side chain includes (meth)acrylic polymers, styryl polymers,polyurethane resins, polyvinyl alcohol resins, polyvinyl formal resins,polyamide resins, polyester resins, epoxy resins and the like.Especially, (meth)acrylic polymers, and styryl polymers are preferred,more preferably (meth)acrylic polymers. The repeating unit (a1) having astructure represented by formula (a1-1) in a side chain is preferably arepeating unit represented by formula (A1) below:

In formula (A1), R^(a) to R^(c) each independently represent a hydrogenatom, C1-6 alkyl or halogen atom. The repeating unit (a1) represents astructure represented by formula (a1-1) above, and is attached to acarbon atom on the main chain of formula (A1) at the point indicated bythe asterisk (*) in formula (a1-1) above.

In the specific polymer compound of the present invention, theproportion of the repeating unit (a1) having a structure represented byformula (a1-1) above is preferably in the range of 1 to 99 mol %, morepreferably in the range of 1 to 90 mol %, even more preferably in therange of 1 to 80 mol % based on the total repeating units to improvestaining resistance and developability.

Preferably, the unit having a structure represented by formula (a1-1)above has a structure generated by the action of a reactive reagent on apolymer containing a repeating unit represented by the formula below ina side chain. The structure of formula (a1-1) above can readily beobtained by the action of a reactive reagent such as, e.g., an acidhalide, acid anhydride, mixed acid anhydride, isocyanic acid compound,epoxy compound, sulfonyl halide compound or alkyl halide compound or thelike on the structure represented by formula (a1-0) above.

In the formula above, L¹, Z¹ and R¹ have the same meanings as definedfor L-, Z¹ and R¹ in formula (a1-1) above.

The reactive reagent is preferably a compound of formula (b-1) orformula (b-2) below.

In formula (b-1) and formula (b-2), R¹¹¹ represents a halogen atom, anoptionally substituted C1-8 alkoxy, or —OSOR¹¹². R¹¹² represents anoptionally substituted C1-8 alkyl. R¹²¹ to R¹²⁹ each independentlyrepresent a hydrogen atom, halogen atom or C1-8 alkyl.Preferably, R¹¹¹ is a C3-8 alkoxy or halogen atom, more preferably ahalogen atom because of the reactivity with the primary or secondaryamino group in formula (a1-1). Preferably, R¹¹² is C1-5 alkyl, morepreferably C1-3 alkyl. Preferably, R¹²¹ to R¹²⁹ each independentlyrepresent a hydrogen atom, or C1-3 alkyl, more preferably a hydrogenatom, or methyl.

The reaction with formula (b-1) or formula (b-2) can be performed in notonly aprotic solvents but also protic solvents because of highreactivity of the amino group. To promote the reaction, a catalyst maybe used as appropriate. The catalyst used may be any one that activatesthe amino group or formula (b-1) or formula (b-2).

(a2) Repeating unit having at least one functional group interactingwith the substrate surface:

The copolymer (A) is characterized in that it comprises (a2) a repeatingunit having at least one of the structures represented by formulae(a2-1), (a2-2), (a2-3), (a2-4), (a2-5) and (a2-6) below in a side chain(hereinafter also referred to as a “repeating unit having at least onefunctional group interacting with the substrate surface).

In formulae (a2-1) to (a2-6), M¹ to M⁸ each independently represent ahydrogen atom, a metal atom contained in an alkali metal or an alkalineearth metal or ammonium. R⁴¹ to R⁴⁶ each independently represent ahydrogen atom or alkyl. Y²¹ to Y²⁶ represent a single bond, or adivalent linking group selected from the group consisting of —CO—, —O—,—NH—, a divalent aliphatic group, a divalent aromatic group and acombination thereof. The asterisk (*) indicates the point of attachmentto the main chain of the polymer compound.

In the formulae above, R⁴¹ to R⁴⁶ preferably each independentlyrepresent a hydrogen atom or C1-10 alkyl. The alkyls represented by R⁴¹to R⁴⁶ include methyl, ethyl, propyl, octyl, isopropyl, t-butyl,isopentyl, 2-ethylhexyl, 2-methylhexyl, cyclopentyl and the like.

In the formulae above, Y²¹ to Y²⁶ each independently represent a singlebond, or a divalent linking group selected from the group consisting of—CO—, —O—, —NH—, a divalent aliphatic group, a divalent aromatic groupand a combination thereof.

Specific examples of Y²¹ to Y²⁶ consisting of the combinations describedabove are shown below. In the examples below, each group is attached tothe main chain at the left end.

L1: —CO—O— a divalent aliphatic group-L2: —CO—O— a divalent aromatic group-L3: —CO—NH— a divalent aliphatic group-L4: —CO—NH— a divalent aromatic group-.

The divalent aliphatic group here refers to alkylene, substitutedalkylene, alkenylene, substituted alkenylene, alkynylene, substitutedalkynylene or polyalkyleneoxy. Among others, alkylene, substitutedalkylene, alkenylene, and substituted alkenylene are preferred, morepreferably alkylene and substituted alkylene.

The divalent aliphatic group preferably has a chain structure to a ringstructure, more preferably has a straight-chain structure to a branchedchain structure. The divalent aliphatic group preferably contains 1 to20, more preferably 1 to 15, even more preferably 1 to 12, still morepreferably 1 to 10, most preferably 1 to 8 carbon atoms. Examples ofsubstituents on the divalent aliphatic group include halogen atoms (F,Cl, Br, I), hydroxy, carboxy, amino, cyano, aryl, alkoxy, aryloxy, acyl,acyloxy, monoalkylamino, dialkylamino, arylamino and diarylamino and thelike.

The divalent aromatic group refers to a divalent monocyclic orpolycyclic aromatic hydrocarbon group. Specific examples of the divalentaromatic group include, for example, 1,2-phenylene, 1,3-phenylene,1,4-phenylene, biphenyl-4,4′-diyl, diphenylmethane-4,4′-diyl,3,3′-dimethylbiphenyl-4,4′-diyl, 1,2-naphthalene, 1,5-naphthalene,2,6-naphthalene and the like. Examples of substituents on the divalentaromatic group include the examples of substituents on the divalentaliphatic group listed above, as well as alkyl.

Preferably, Y²¹ to Y²⁶ represent a single bond, a divalent aromaticgroup, L1, L2, L3 and L4, more preferably a single bond, L1 and L2.

M¹ to M⁸ each independently represent a hydrogen atom, a metal atomcontained in an alkali metal or an alkaline earth metal or ammonium,preferably a hydrogen atom, or a metal atom contained in an alkalinemetal, more preferably a hydrogen atom.

Among the structures represented by formulae (a2-1) to (a2-6) above, thestructure interacting with the substrate surface is preferably astructure represented by formulae (a2-1), (a2-2) and (a2-6) above, morepreferably a structure represented by formula (a2-1) or (a2-2) above toimprove staining resistance and printing durability. Further, M¹ and M²,and M³ and M⁴ are preferably a hydrogen atom, respectively in both ofthe structure represented by formula (a2-1) above and the structurerepresented by formula (a2-2) above.

Further, the functional group interacting with the substrate surface ispreferably the carboxylic acid-containing group, sulfonic acid,phosphoric acid ester or a salt thereof, phosphonic acid or a saltthereof to improve staining resistance and printing durability.

Specifically, the structures represented by formulae (a2-1) to (a2-6)above include the structures shown below, but the present invention isnot limited to the specific examples below. In the formulae below, theasterisk (*) indicates the point of attachment to the main chain of thepolymer compound.

The repeating unit (a2) having at least one structure interacting withthe substrate surface is preferably a repeating unit represented byformula (A2) below.

In formula (A2) above, R_(a)′ to R^(c)′ each independently represent ahydrogen atom, C1-6 alkyl or halogen atom. L⁴ represents a single bondor a divalent linking group. (a2) represents a structure represented byformulae (a2-1) to (a2-6) above, and it is attached to a carbon atom atthe point indicated by the asterisk (*) in formulae (a2-1) to (a2-6).

In the copolymer (A), the proportion of the repeating unit having astructure represented by formulae (a2-1) to (a2-6) (a2) above ispreferably in the range of 1 to 99 mol %, more preferably in the rangeof 1 to 90 mol %, even more preferably in the range of 1 to 80 mol %based on the total repeating units to improve staining resistance anddevelopability.

(a3) Repeating unit having a hydrophilic group in a side chain:

The copolymer (A) preferably comprises (a3) a repeating unit having atleast one hydrophilic group in a side chain to confer highhydrophilicity on the substrate surface of non-image areas. Thehydrophilic group is selected from monovalent or divalent or polyvalenthydrophilic groups capable of readily forming a hydrogen bond/van derWaals bond/ionic bond with a water molecule, specifically includinghydroxy, carboxyl, amino, sulfo, positively or negatively chargedgroups, zwitterionic groups and metal salts thereof and the like. Amongthem, hydroxy, sulfonic acid, alkyleneoxy such as ethyleneoxy andpropyleneoxy, quaternary ammonium, amide, ether bond-containing groups,or salts obtained by neutralizing acid groups such as carboxylic acid,sulfonic acid, phosphoric acid and the like, heterocyclic groupscontaining positively charged nitrogen atoms and the like are preferred,for example. These hydrophilic groups may also be used as the repeatingunit (a2) having a structure interacting with the substrate surface in aside chain.

In the present invention, the repeating unit (a3) having a hydrophilicgroup in a side chain is especially preferably a repeating unit having azwitterionic structure in a side chain to confer high hydrophilicity onthe substrate surface of non-image areas.

In the lithographic printing plate precursor of the present invention,the hydrophilic group contained in the copolymer (A) is especiallypreferably selected from zwitterionic structures represented by formula(a3-1) or (a3-2) below:

In formula (a3-1) above, R³¹ and R³² each independently represent ahydrogen atom, alkyl, alkenyl, alkynyl, aryl, or heterocyclyl, or R³¹and R³² may be joined together to form a ring structure, L³¹ representsa linking group, and A- represents an anion-containing structure. Y³represents a divalent linking group attached to the main chain of thepolymer compound. The asterisk (*) indicates the point of attachment tothe main chain of the polymer compound.

The ring structure formed by R³¹ and R³² together is preferably a 5- to10-membered ring, more preferably a 5- or 6-membered ring, and maycontain a heteroatom such as oxygen atom or the like.

Preferably, R³¹ and R³² contain 1 to 30 carbon atoms, more preferably 1to 20 carbon atoms, especially preferably 1 to 15 carbon atoms, mostpreferably 1 to 8 carbon atoms including carbon atoms of the optionallypresent substituent described below.

Examples of alkyls represented by R³¹ and R³² include methyl, ethyl,propyl, octyl, isopropyl, t-butyl, isopentyl, 2-ethylhexyl,2-methylhexyl, cyclopentyl and the like. Examples of alkenylsrepresented by R³¹ and R³² include vinyl, allyl, prenyl, geranyl, oleyland the like.

Examples of alkynyls represented by R³¹ and R³² include ethynyl,propargyl, trimethylsilylethynyl and the like. Further, examples ofaryls represented by R³¹ and R³² include phenyl, 1-naphthyl, 2-naphthyland the like. Further, examples of heterocyclyls include furanyl,thiophenyl, pyridinyl and the like.

These groups represented by R³¹ and R³² may be further substituted.Examples of substituents include halogen atoms (F, Cl, Br, I), hydroxy,carboxy, amino, cyano, aryl, alkoxy, aryloxy, acyl, alkoxycarbonyl,aryloxycarbonyl, acyloxy, monoalkylamino, dialkylamino, monoarylaminoand diarylamino and the like.

Especially preferred examples of R³¹ and R³² include a hydrogen atom,methyl, or ethyl because of the resulting effect and availability.

The divalent linking group represented by Y³ is a single bond or adivalent linking group selected from the group consisting of —CO—, —O—,—NH—, a divalent aliphatic group, a divalent aromatic group and acombination thereof.

Specific examples of Y³ consisting of the combination described aboveare shown below. In the examples below, each group is attached to themain chain at the left end.

L101: —CO—O— a divalent aliphatic group-L102: —CO—O— a divalent aromatic group-L103: —CO—NH— a divalent aliphatic group-L104: —CO—NH— a divalent aromatic group-L105: —CO— a divalent aliphatic group-L106: —CO— a divalent aromatic group-L107: —CO— a divalent aliphatic group-CO—O— a divalent aliphatic group-L108: —CO— a divalent aliphatic group-C—CO— a divalent aliphatic group-L109: —CO— a divalent aromatic group-CO—O— a divalent aliphatic group-L110: —CO— a divalent aromatic group-O—CO— a divalent aliphatic group-L111: —CO— a divalent aliphatic group-CO—O— a divalent aromatic group-L112: —CO— a divalent aliphatic group-O—CO— a divalent aromatic group-L113: —CO— a divalent aromatic group-CO—O— a divalent aromatic group-L114: —CO— a divalent aromatic group-O—CO— a divalent aromatic group-L115: —CO—C— a divalent aromatic group-O—CO—NH— a divalent aliphaticgroup-L116: —CO—O— a divalent aliphatic group-C—CO—NH— a divalent aliphaticgroup-.

The divalent aliphatic group and the divalent aromatic group describedabove refer to include the linking groups mentioned as examples of thedivalent aliphatic group containing 1 to 14 carbon atoms for Z¹, and thelinking groups mentioned as examples of the divalent aromatic groupcontaining 6 to 14 carbon atoms for L¹, respectively. Examples ofsubstituents on the divalent aliphatic group and the divalent aromaticgroup include the substituents with which the groups represented by R³¹and R³² may be further substituted.

Among others, Y³ is preferably a single bond, —CO—, a divalent aliphaticgroup, a divalent aromatic group, or L101 to L104 shown above. Further,Y¹ is preferably L¹⁰¹ or L103 shown above, more preferably L103 toimprove staining resistance. Further, the divalent aliphatic group ofL103 is preferably a straight-chain alkylene containing 2 to 4 carbonatoms, most preferably a straight-chain alkylene containing 3 carbonatoms for convenience of synthesis.

L³¹ represents a linking group, preferably a linking group selected fromthe group consisting of —CO—, —O—, —NH—, a divalent aliphatic group, adivalent aromatic group and a combination thereof, and preferablycontains 30 or less carbon atoms including carbon atoms of theoptionally present substituents described below. Specific examplesthereof include alkylene (preferably containing 1 to 20 carbon atoms,more preferably 1 to 10 carbon atoms), and arylene (preferablycontaining 5 to 15 carbon atoms, more preferably 6 to 10 carbon atoms)such as phenylene, xylylene and the like. Among others, L³¹ ispreferably a straight-chain alkylene containing 3 to 5 carbon atoms,more preferably a straight-chain alkylene containing 4 or 5 carbonatoms, most preferably a straight-chain alkylene containing 4 carbonatoms to improve staining resistance. Specific examples of L³¹ include,for example, the following linking groups:

These linking groups may be further substituted. Examples ofsubstituents include halogen atoms (F, Cl, Br, I), hydroxy, carboxy,amino, cyano, aryl, alkoxy, aryloxy, acyl, alkoxycarbonyl,aryloxycarbonyl, acyloxy, monoalkylamino, dialkylamino, monoarylaminoand diarylamino and the like.

In formula (a1-1) above, A⁻ preferably represents carboxylate,sulfonate, phosphate, phosphonate, or phosphinate.

Specifically, the following anions are included.

To improve staining resistance, A⁻ is most preferably sulfonate.Further, a preferred combination of L³¹ and A⁻ in formula (a1-1) aboveis a combination of a straight-chain alkylene containing 4 or 5 carbonatoms and sulfonate, most preferably a combination of a straight-chainalkylene containing 4 carbon atoms and sulfonate.

In a preferred combination, Y³ is L101 or L103 shown above, R³¹ and R³²are ethyl or methyl, L³¹ is a straight-chain alkylene containing 4 or 5carbon atoms, and A⁻ is sulfonate. In a more preferred combination, Y³is L¹⁰³ shown above, R³¹ and R³² are methyl, L³¹ is a straight-chainalkylene containing 4 carbon atoms, and A⁻ is sulfonate. Thezwitterionic structure represented by formula (a3-1) above specificallyincludes the structures shown below. In the formulae below, the asterisk(*) indicates the point of attachment to the main chain of the copolymer(A).

Next, the zwitterionic structure represented by formula (a3-2) below isexplained.

In formula (a3-2), L³² represents a divalent linking group, and E⁺represents a cation-containing structure. Y⁴ represents a single bond,or a divalent linking group selected from the group consisting of —CO—,—O—, —NH—, a divalent aliphatic group, a divalent aromatic group and acombination thereof. The asterisk (*) indicates the point of attachmentto the main chain of the copolymer.

Also in formula (a3-2) above, L³² represents a linking group preferablyselected from the group consisting of —CO—, —O—, —NH—, a divalentaliphatic group, a divalent aromatic group and a combination thereof.Specific examples and preferred examples thereof are the same asmentioned above for the linking group represented by L³¹. Y⁴ has thesame meaning as defined for Y³ in formula (a3-2) above, and also coverssimilar preferred examples. E⁺ represents a cation-containing structure,preferably a structure containing ammonium, phosphonium, iodonium, orsulfonium, more preferably a structure containing ammonium orphosphonium, especially preferably a structure containing ammonium.Examples of cation-containing structures include trimethylammonio,triethylammonio, tributylammonio, benzyldimethylammonio,diethylhexylammonio, (2-hydroxyethyl)dimethylammonio, pyridinio,N-methylimidazolio, N-acridinio, trimethylphosphonio,triethylphosphonio, triphenylphosphonio and the like.

In a most preferred combination of L³², Y⁴ and E⁺, L³² is an alkylenecontaining 2 to 4 carbon atoms, Y⁴ is L101 or L103 shown above, and E⁺is trimethylammonio or triethylammonio. The zwitterionic structurerepresented by formula (a3-2) specifically includes the structures shownbelow. In the formulae below, the asterisk (*) indicates the point ofattachment to the main chain of the copolymer (A).

In the present invention, the repeating unit having a zwitterionicstructure is preferably represented by (A3) specifically.

wherein R²⁰¹ to R²⁰³ each independently represent a hydrogen atom, C1-6alkyl or halogen atom. G represents a divalent linking group having ahydrophilic group, or a structure represented by formula (a3-1) or(a3-2), and is attached to a carbon atom at the point indicated by theasterisk (*) in formulae (a3-1) to (a3-2).

In formula (A3) above, the side chain G is especially preferably astructure represented by formula (a3-1).

In the present invention, the proportion of the repeating unit (a3)having a hydrophilic group in a side chain based on the total repeatingunits constituting the copolymer (A) is preferably in the range of 1 to70 mol %, more preferably in the range of 1 to 50 mol %, even morepreferably in the range of 1 to 30 mol % based on the total repeatingunits to improve staining resistance and developability.

Extra repeating unit:

Further, the copolymer (A) may comprise an extra repeating unit otherthan the repeating units described above (hereinafter also referred toas an “extra repeating unit”) as a component of a copolymer. Extrarepeating units that may be contained as such repeating units includerepeating units derived from various known monomers.Preferred examples include repeating units derived from known monomerssuch as acrylic acid esters, methacrylic acid esters, acrylamides,methacrylamides, vinyl esters, styrenes, acrylic acid, methacrylic acid,acrylonitrile, maleic anhydride, maleimide and the like. Variousproperties of the layers such as film-forming properties, film strength,hydrophilicity, hydrophobicity, solubility, reactivity, stability andthe like can be improved or controlled as appropriate by introducing theextra repeating unit into the copolymer (A).Among others, monomers selected from acrylic acid esters, methacrylicacid esters, N,N-2-substituted acrylamides, N,N-2-substitutedmethacrylamides, styrenes, acrylonitriles, methacrylonitriles and thelike are included.

Specific examples include, for example, acrylic acid esters such asalkyl acrylate (wherein the alkyl group preferably contains 1 to 20carbon atoms) (specifically, e.g., methyl acrylate, ethyl acrylate,propyl acrylate, butyl acrylate, amyl acrylate, ethylhexyl acrylate,octyl acrylate, t-octyl acrylate, chloroethyl acrylate,2,2-dimethylhydroxypropyl acrylate, 5-hydroxypentyl acrylate,trimethylolpropane monoacrylate, pentaerythritol monoacrylate, glycidylacrylate, benzyl acrylate, methoxybenzyl acrylate, furfuryl acrylate,tetrahydrofurfuryl acrylate and the like), and aryl acrylate (e.g.,phenyl acrylate and the like); methacrylic acid esters such as alkylmethacrylate (wherein the alkyl group preferably contains 1 to 20 carbonatoms) (e.g., methyl methacrylate, ethyl methacrylate, propylmethacrylate, isopropyl methacrylate, amyl methacrylate, hexylmethacrylate, cyclohexyl methacrylate, benzyl methacrylate, chlorobenzylmethacrylate, octyl methacrylate, 4-hydroxybutyl methacrylate,5-hydroxypentyl methacrylate, 2,2-dimethyl-3-hydroxypropyl methacrylate,trimethylolpropane monomethacrylate, pentaerythritol monomethacrylate,glycidyl methacrylate, furfuryl methacrylate, tetrahydrofurfurylmethacrylate and the like), and aryl methacrylate (e.g., phenylmethacrylate, cresyl methacrylate, nephthyl methacrylate and the like);styrenes such as styrene, alkylstyrene (e.g., methylstyrene,dimethylstyrene, trimethylstyrene, ethylstyrene, diethylstyrene,isopropylstyrene, butylstyrene, hexylstyrene, cyclohexylstyrene,decylstyrene, benzylstyrene, chloromethylstyrene,trifluoromethylstyrene, etoxymethylstyrene, acetoxymethylstyrene and thelike), alkoxystyrene (e.g., methoxystyrene, 4-methoxy-3-methylstyrene,dimethoxystyrene and the like), and halogenated styrene (e.g.,chlorostyrene, dichlorostyrene, trichlorostyrene, tetrachlorostyrene,pentachlorostyrene, bromostyrene, dibromostyrene, iodostyrene,fluorostyrene, trifluorostyrene, 2-bromo-4-trifluoromethylstyrene,4-fluoro-3-trifluoromethylstyrene and the like); acrylonitrile,methacrylonitrile, methacrylic acid, acrylic acid,2-acrylamide-2-methylpropanesulfonic acid and the like.

In the copolymer (A), the proportion of the extra repeating unit ispreferably 0 to 60 mol %, more preferably 0 to 40 mol %, even morepreferably 0 to 30%.

<<Copolymers of the Present Invention>>

Among the copolymers (A) that can be used in these lithographic printingplate precursors of the present invention, copolymers of the presentinvention are polymer compounds having the characteristic structure asfollows. The copolymers of the present invention are characterized inthat they comprise:(a1) a repeating unit having a structure represented by formula (a1-1)below in a side chain;(a2) a repeating unit having at least one of the structures representedby formulae (a2-1), (a2-1), (a2-3), (a2-4), (a2-5) and (a2-6) in a sidechain; and(a3′) a repeating unit having a zwitterionic structure represented byformula (a3-1) or (a3-2) below in a side chain.

In formula (a1-1), L¹ represents a single bond, a divalent aromaticgroup containing 6 to 14 carbon atoms, —C(═O)—O—, or —C(═O)—NR²—(wherein R² represents a hydrogen atom, alkyl or aryl). Z¹ represents adivalent linking group selected from the group consisting of a divalentaliphatic group containing 1 to 14 carbon atoms, a divalent aromaticgroup containing 6 to 14 carbon atoms, —NH—, —O—, —S— and a combinationthereof, provided that both ends are not —NH—, —O— or —S—, and when L¹is a divalent aromatic group containing 6 to 14 carbon atoms, Z¹ is nota divalent aromatic group containing 6 to 14 carbon atoms, and thedivalent aliphatic group, divalent aromatic group and —NH— may have asubstituent instead of a hydrogen atom. R¹ represents a hydrogen atom,alkyl, aryl, heterocyclyl, sulfo, alkylsulfonyl and arylsulfonyl. R¹represents a hydrogen atom, alkyl, aryl, heterocyclyl, sulfo,alkylsulfonyl and arylsulfonyl. R²¹, R²² and R²³ each independentlyrepresent a hydrogen atom, halogen atom or C1-8 alkyl. The asterisk (*)indicates the point of attachment to the main chain of the copolymer.

wherein M¹ to M⁸ each independently represent a hydrogen atom, a metalatom contained in an alkali metal or an alkaline earth metal orammonium. R⁴¹ to R⁴⁶ each independently represent a hydrogen atom oralkyl. Y²¹ to Y²⁶ represent a single bond, or a divalent linking groupselected from the group consisting of —CO—, —O—, —NH—, a divalentaliphatic group, a divalent aromatic group and a combination thereof.The asterisk (*) indicates the point of attachment to the main chain ofthe polymer compound.

In formula (a3-1), R³¹ and R³² each independently represent a hydrogenatom, alkyl, alkenyl, alkynyl, aryl, or heterocyclyl, or R³¹ and R³² maybe joined together to form a ring structure, L³¹ represents a linkinggroup, and A- represents an anion-containing structure. Y³ represents asingle bond, or a divalent linking group selected from the groupconsisting of, —CO—, —O—, —NH—, a divalent aliphatic group, a divalentaromatic group and a combination thereof. The asterisk (*) indicates thepoint of attachment to the main chain of the polymer compound.

In formula (a3-2) above, L³² represents a linking group, and E+represents a cation-containing structure. Y⁴ represents a single bond,or a divalent linking group selected from the group consisting of —CO—,—O—, —NH—, a divalent aliphatic group, a divalent aromatic group and acombination thereof. The asterisk (*) indicates the point of attachmentto the main chain of the polymer compound.

(Weight Average Molecular Weight)

The weight average molecular weight (Mw) of the copolymer (A) can beappropriately selected depending on the performance design of thelithographic printing plate precursor. To improve printing durabilityand staining resistance, the weight average molecular weight ispreferably 2,000 to 1,000,000, more preferably 2,000 to 500,000, mostpreferably 8,000 to 300,000.

Specific examples of the copolymer (A) are shown below along with theirweight average molecular weights, but the present invention is notlimited to these examples. It should be noted that the composition ratioof the polymer structures are expressed in mass percentage.

<<Processes for Preparing the Copolymers of the Present Invention>>

The specific polymer compounds (copolymers (A)) and, among others, thecopolymers of the present invention having a characteristic structurecan be synthesized by known methods, but preferably by using radicalpolymerization followed by ureation reaction using the amino group in apolymer side chain and an isocyanate having a radically polymerizablereactive group.

Typical techniques for radical polymerization are described in, forexample, “New Polymer Experimental Chemistry, vol. 3” (Edited by theSociety of Polymer Science, Japan, published by KYORITSU SHUPPAN CO.,LTD., Mar. 28, 1996); “Synthesis and Reaction of Polymers, vol. 1”(Edited by the Society of Polymer Science, Japan, published by KYORITSUSHUPPAN CO., LTD., May 1992); “New Textbook of Experimental Chemistry,vol. 19, Polymer Chemistry (I) (Edited by the Chemical Society of Japan,published by Maruzen Company, Limited, Nov. 20, 1980); “Textbook ofMaterial Engineering, Polymer Synthetic Chemistry” (published by TokyoDenki University Press, September 1995) and the like, and thesetechniques can be applied.

The processes for preparing the copolymers of the present invention arecharacterized by preparing a unit having a structure represented byformula (a1-1) above by using the reactive reagents. Details are asdescribed for the generation of the unit having a structure representedby formula (a1-1) above.

Thus, the processes for preparing the copolymers of the presentinvention are characterized in that they comprise introducing (a1) therepeating unit having a structure represented by formula (a1-1) above ina side chain by reacting a polymer comprising:(a0) a repeating unit having a structure represented by formula (a1-0)below in a side chain;(a2) the repeating unit having a structures represented by any one offormulae (a2-1), (a2-1), (a2-3), (a2-4), (a2-5) and (a2-6) above in aside chain; and(a3′) the repeating unit having a zwitterionic structure represented byformula (a3-1) or (a3-2) above in a side chain;with a compound represented by formula (b-1) or (b-2) below.

In formula (a1-0), L¹⁰¹ represents a single bond, a divalent aromaticgroup containing 6 to 14 carbon atoms, —C(═O)—O—, or —C(═O)—NR¹⁰²—(wherein R¹⁰² represents a hydrogen atom, alkyl or aryl). Z¹⁰¹represents a divalent linking group selected from the group consistingof a divalent aliphatic group containing 1 to 14 carbon atoms, adivalent aromatic group containing 6 to 14 carbon atoms, —NH—, —O—, —S—and a combination thereof, provided that both ends are not —NH—, —O— or—S—, and when L¹ is a divalent aromatic group containing 6 to 14 carbonatoms, Z¹ is not a divalent aromatic group containing 6 to 14 carbonatoms, and the divalent aliphatic group, divalent aromatic group and—NH— may have a substituent instead of a hydrogen atom. R¹⁰¹ representsa hydrogen atom, alkyl, aryl, heterocyclyl, sulfo, alkylsulfonyl andarylsulfonyl. The asterisk (*) indicates the point of attachment to themain chain of the copolymer.

In formulae (b-1) and (b-2), R¹¹¹ represents a halogen atom, anoptionally substituted C1-8 alkoxy, or —OSOR¹¹². R¹¹² represents anoptionally substituted C1-8 alkyl. R¹²¹ to R¹²⁹ each independentlyrepresent a hydrogen atom, halogen atom or C1-8 alkyl.

In formula (a1-0) above, preferred ranges of L¹⁰¹, R¹⁰², Z¹⁰¹, and R¹⁰¹are similar to the preferred ranges of L¹, R¹, Z¹, and R² in formula(a1-1) above.

(B) Polymerization Initiator

The photosensitive layer of the present invention preferably contains apolymerization initiator (hereinafter also referred to as an “initiatorcompound”). In the present invention, a radical polymerization initiatoris preferably used.

The initiator compound may be arbitrarily selected from compounds knownamong those skilled in the art without limitation. Specific examplesinclude trihalomethyl compound, carbonyl compound, organic peroxide, azocompound, azide compound, metallocene compound, hexaarylbiimidazolecompound, organic boron compound, disulfone compound, oxim estercompound, onium salt, and iron arene complex. In particular, theinitiator compound is preferably at least one species selected from thegroup consisting of hexaarylbiimidazole compound, onium salt,trihalomethyl compound and metallocene compound, and is particularlyhexaarylbiimidazole compound, or onium salt. Two or more species of themmay be used in combination as the polymerization initiator.

The hexaarylbiimidazole compound is exemplified by lophine dimersdescribed in European Patent Nos. 24,629 and No. 107,792, and U.S. Pat.No. 4,410,621, which are exemplified by2,2′-bis(o-chlorophenyl)-4,4′,5,5′-tetraphenylbiimidazole,2,2′-bis(o-bromophenyl)-4,4′,5,5′-tetraphenylbiimidazole,2,2′-bis(o,p-dichlorophenyl)-4,4′,5,5′-tetraphenylbiimidazole,2,2′-bis(o-chlorophenyl)-4,4′,5,5′-tetra(m-methoxyphenyl)biimidazole,2,2′-bis(o,o′-dichlorophenyl)-4,4′,5,5′-tetraphenylbiimidazole,2,2′-bis(o-nitrophenyl)-4,4′,5,5′-tetraphenylbiimidazole,2,2′-bis(o-methylphenyl)-4,4′,5,5′-tetraphenylbiimidazole, and2,2′-bis(o-trifluoromethylphenyl)-4,4′,5,5′-tetraphenyl biimidazole. Itis particularly preferable that the hexaarylbiimidazole compound is usedin combination with a sensitizing dye which shows maximum absorption inthe wavelength range from 300 to 450 nm.

The onium salt is exemplified by diazonium salts described in S.I.Schlesinger, Photogr. Sci. Eng., 18, 387 (1974), T. S. Bal et al.,Polymer, 21, 423 (1980), and Japanese Laid-Open Patent Publication No.H05-158230; ammonium salts described for example in U.S. Pat. No.4,069,055, and Japanese Laid-Open Patent Publication No. H04-365049;phosphonium salts described in U.S. Pat. Nos. 4,069,055 and 4,069,056;iodonium salts described in European Patent Nos. 104,143, United StatesPatent Publication No. 2008/0311520, Japanese Laid-Open PatentPublication Nos. H02-150848 and 2008-195018, and J. V. Crivello et al.,Macromolecules, 10(6), 1307 (1977); sulfonium salts described inEuropean Patent No. 370,693, ibid. No. 233,567, ibid. No. 297,443, ibid.No. 297,442, U.S. Pat. No. 4,933,377, ibid. U.S. Pat. No. 4,760,013,ibid. U.S. Pat. No. 4,734,444 and ibid. U.S. Pat. No. 2,833,827, andGerman Patent No. 2,904,626, ibid. No. 3,604,580 and ibid. No.3,604,581; selenonium salts described in J. V. Crivello et al., J.Polymer Sci., Polymer Chem. Ed., 17, 1047 (1979); arsonium saltsdescribed in C. S. Wen et al., The Proc. Conf. Rad. Curing ASIA, p 478,Tokyo, October(1988); and azinium salts described in Japanese Laid-OpenPatent Publication No. 2008-195018.

Among them, more preferable examples include iodonium salt, sulfoniumsalt and azinium salts. Specific examples of these compounds will beshown below, without limiting the present invention.

The iodonium salt is preferably diphenyliodonium salt, more preferablydiphenyliodonium salt substituted by an electron donor group such asalkyl group or alkoxyl group, and still more preferably asymmetricdiphenyliodonium salts. Specific examples include diphenyliodoniumhexafluorophosphate, 4-methoxyphenyl-4-(2-methylpropyl)phenyliodoniumhexafluorophosphate, 4-(2-methylpropyl)phenyl-p-tolyliodoniumhexafluorophosphate, 4-hexyloxyphenyl-2,4,6-trimethoxyphenyliodoniumhexafluorophosphate, 4-hexyloxyphenyl-2,4-diethoxyphenyliodoniumtetrafluoroborate, 4-octyloxyphenyl-2,4,6-trimethoxyphenyliodonium1-perfluorobutanesulfonate,4-octyloxyphenyl-2,4,6-trimethoxyphenyliodonium hexafluorophosphate, andbis(4-t-butylphenyl)iodonium tetraphenylborate.

Examples of the sulfonium salt include triphenylsulfoniumhexafluorophosphate, triphenylsulfonium benzoylformate,bis(4-chlorophenyl)phenylsulfonium benzoylformate,bis(4-chlorophenyl)-4-methylphenylsulfonium tetrafluoroborate,tris(4-chlorophenyl)sulfonium 3,5-bis(methoxycarbonyl)benzenesulfonate,and tris(4-chlorophenyl)sulfonium hexafluorophosphate.

Examples of the azinium salt include 1-cyclohexylmethyloxypyrydiniumhexafluorophosphate, 1-cyclohexyloxy-4-phenylpyrydiniumhexafluorophosphate, 1-ethoxy-4-phenylpyrydinium hexafluorophosphate,1-(2-ethylhexyloxy)-4-phenylpyrydinium hexafluorophosphate,4-chloro-1-cyclohexylmethyloxypyrydinium hexafluorophosphate,1-ethoxy-4-cyanopyrydinium hexafluorophosphate,3,4-dichloro-1-(2-ethylhexyloxy)pyrydinium hexafluorophosphate,1-benzyloxy-4-phenylpyrydinium hexafluorophosphate,1-phenetyloxy-4-phenylpyrydinium hexafluorophosphate,1-(2-ethylhexyloxy)-4-phenylpyrydinium p-toluenesulfonate,1-(2-ethylhexyloxy)-4-phenylpyrydinium perfluorobutanesulfonate,1-(2-ethylhexyloxy)-4-phenylpyrydinium bromide, and

1-(2-ethylhexyloxy)-4-phenylpyrydinium tetrafluoroborate.

It is particularly preferable that the onium salt is used in combinationwith an infrared absorber which shows maximum absorption in thewavelength range from 750 to 1400 nm.

Besides them, also polymerization initiators described in paragraphs[0071] to [0129] of Japanese Laid-Open Patent Publication No.2007-206217 are preferably used.

The polymerization initiator is preferably used alone, or in combinationof two or more species.

The content of the polymerization initiator in the photosensitive layeris preferably 0.01 to 20% by mass relative to the total solid content ofthe image recording layer, more preferably 0.1 to 15% by mass, and stillmore preferably 1.0 to 10% by mass.

(C) Polymerizable Compound

The polymerizable compound used for the image recording layer is anaddition polymerizable compound having at least one ethylenicunsaturated double bond, and is selected from compounds having at leastone, and preferably two, terminal ethylenic unsaturated bonds. Thesecompounds typically have any of chemical forms including monomer;prepolymer such as dimer, trimer and oligomer; and mixtures of them.Examples of the monomer include unsaturated carboxylic acid (forexample, acrylic acid, methacrylic acid, itaconic acid, crotonic acid,isocrotonic acid, maleic acid), esters of them, and amides of them. Morepreferable examples include esters formed between unsaturated carboxylicacid and polyhydric alcohol compound, and amides formed betweenunsaturated carboxylic acid and polyvalent amine compound. Still otherpreferable examples include adducts of unsaturated carboxylate esters oramides having nucleophilic substituent group such as hydroxy group,amino group, mercapto group or the like, formed together withmonofunctional or polyfunctional isocyanates or epoxys; and dehydrationcondensation product formed together with monofunctional orpolyfunctional carboxylic acid. Still other preferable examples includeadducts of unsaturated carboxylate esters or amides having electrophilicsubstituent group such as isocyanate group and epoxy group, formedtogether with monofunctional or polyfunctional alcohols, amines, orthiols; and substitution products of unsaturated carboxylate esters oramides having eliminative substituent group such as halogen group andtosyloxy group, formed together with monofunctional or polyfunctionalalcohols, amines, or thiols.

Also compounds obtained by replacing the above-described unsaturatedcarboxylic acid with unsaturated phosphonic acid, styrene, vinyl etheror the like are also adoptable. These compounds are disclosed inPublished Japanese Translation of PCT International Publication forPatent Application No. 2006-508380, Japanese Laid-Open PatentPublication Nos. 2002-287344, 2008-256850, 2001-342222, H09-179296,H09-179297, H09-179298, 2004-294935, 2006-243493, 2002-275129,2003-64130, 2003-280187, and H10-333321.

Specific examples of the monomer in the form of acrylate ester formedbetween polyhydric alcohol compound and unsaturated carboxylic acidinclude ethylene glycol diacrylate, 1,3-butanediol diacrylate,tetramethylene glycol diacrylate, propylene glycol diacrylate,trimethylolpropane triacrylate, hexanediol diacrylate, tetraethyleneglycol diacrylate, pentaerythritol tetraacrylate, sorbitol triacrylate,isocyanurate ethylene oxide (EO)-modified triacrylate, and polyesteracrylate oligomer. Examples of methacrylate ester include tetramethyleneglycol dimethacrylate, neopentyl glycol dimethacrylate,trimethylolpropane trimethacrylate, ethylene glycol dimethacrylate,pentaerythritol trimethacrylate, bis[p-(3-methacryloxy-2-hydroxypropoxy)phenyl]dimethylmethane, andbis-[p-(methacryloxyethoxy)phenyl]dimethylmethane. Specific examples ofthe monomer in the form of amide formed between polyvalent aminecompound and unsaturated carboxylic acid include methylenebisacrylamide, methylene bismethacrylamide, 1,6-hexamethylenebisacrylamide, 1,6-hexamethylene bismethacrylamide, diethylenetriaminetrisacrylamide, xylylene bisacrylamide, and xylylene bismethacrylamide.

Also urethane-based addition polymerizable compound, obtainable byaddition polymerization between the isocyanate and hydroxy group, ispreferable. Preferable examples of this sort of compound include vinylurethane compound having two or more polymerizable vinyl groups per onemolecule, which is obtainable by addition reaction between a vinylmonomer having a hydroxy group represented by the formula (P) below, anda polyisocyanate compound having two or more isocyanate groups per onemolecule, as described in Examined Japanese Patent Publication No.S48-41708.

CH₂═C(R¹⁰⁴)COOCH₂CH(R¹⁰⁵)OH  (P)

(where, each of R¹⁰⁴ and R¹⁰⁵ represents H or CH₃.)

Other preferable examples include urethane acrylates described inJapanese Laid-Open Patent Publication No. $51-37193, Examined JapanesePatent Publication No. H02-32293, ibid. H02-16765, Japanese Laid-OpenPatent Publication No. 2003-344997, ibid. No. 2006-65210; urethanecompounds having ethylene oxide-based skeleton described in ExaminedJapanese Patent Publication Nos. 358-49860, ibid. S56-17654, ibid.362-39417, ibid. No. S62-39418, Japanese Laid-Open Patent PublicationNo. 2000-250211, ibid. No. 2007-94138; and urethane compound havinghydrophilic group described in U.S. Pat. No. 7,153,632, PublishedJapanese Translation of PCT International Publication for PatentApplication No. H08-505958, Japanese Laid-Open Patent Publication No.2007-293221, and ibid. No. 2007-293223.

Among them, for the lithographic printing plate precursor adapted to theon-machine development, isocyanurate of ethylene oxide-modified acrylatesuch as tris(acryloyloxyethyl)isocyanurate, andbis(acryloyloxyethyl)hydroxyethyl isocyanurate are particularlypreferable, from the viewpoint of good balance between hydrophilicitycontributive to the on-press developability and polymerizabilitycontributive to the printing durability.

Structure of the polymerizable compound (C), and method of use,including whether it is used alone or in combination with other species,or amount of use, may be arbitrarily determined depending on a finaldesired goal of performance design of lithographic printing plateprecursor. The content of the polymerizable compound (C) is preferably 5to 75% by mass of the total solid content of the image recording layer,more preferably 25 to 70% by mass, and particularly 30 to 60% by mass.

(D) Binder

The binder (D) contained in the photosensitive layer of the lithographicprinting plate precursor according to the present invention is selectedfrom those capable of keeping the photosensitive layer component on thesupport, and removable by the developer. Examples of the binder (E)include (meth)acrylic polymer, polyurethane resin, polyvinyl alcoholresin, polyvinyl butyral resin, polyvinyl formal resin, polyamide resin,polyester resin, and epoxy resin. In particular, (meth)acrylic polymer,polyurethane resin, and polyvinyl butyral resin are preferably used.More preferable examples include (meth)acrylic polymer, polyurethaneresin, and polyvinyl butyral resin.

In the present invention, “(meth)acrylic polymer” means copolymerhaving, as a polymerizable component, (meth)acrylic acid derivative suchas (meth)acrylic acid, (meth)acryliate ester (alkyl ester, aryl ester,allylester, etc.), (meth)acrylamide and (meth)acrylamide derivative.“Polyurethane resin” means polymer produced by condensation reactionbetween a compound having two or more isocyanate groups and a compoundhaving two or more hydroxy groups. “Polyvinyl butyral resin” meanspolymer synthesized by allowing polyvinyl alcohol obtained by partiallyor totally saponifying polyvinyl acetate to react with butyl aldehydeunder an acidic condition (acetal forming reaction), which also includespolymer having introduced therein acid group and so forth, obtained byallowing the residual hydroxy group to react with a compound having acidgroup.

One preferable example of the (meth)acrylic polymer is a copolymerhaving a repeating unit which contains an acid group. The acid group isexemplified by carboxylate group, sulfonate group, phosphonate group,phosphate group, and sulfonamide group, wherein carboxylate group isparticularly preferable. The repeating unit having acid group preferablyused herein includes a repeating unit derived from (meth)acrylic acid,or a unit represented by the formula (I) below:

In the formula (I), R²¹¹ represents a hydrogen atom or methyl group,R²¹² represents a single bond or n₂₁₁ monovalent linking groups. A²¹¹represents an oxygen atom or —NR²¹³—, and R²¹³ represents a hydrogenatom or C₁₋₁₀ monovalent hydrocarbon group. n₂₁₁ represents an integerfrom 1 to 5.

The linking group represented by R²¹² in the formula (I) is composed ofhydrogen atom, carbon atom, oxygen atom, nitrogen atom, sulfur atom andhalogen atom, with a total number of atoms of preferably 1 to 80. Morespecifically, the alkylene group, substituted alkylene group, arylenegroup, and substituted arylene group are exemplified. A plurality ofthese divalent groups may be linked with any of amide bond, ether bond,urethane bond, urea bond and ester bond. R²¹² preferably has a structurein which a plurality of single bonds, alkylene groups, substitutedalkylene groups and alkylene groups and/or substituted alkylene groupsare linked with any of amide bond, ether bond, urethane bond, urea bond,and ester bond; more preferably has a structure in which a plurality ofsingle bonds, C₁₋₅ alkylene groups, C₁₋₅ substituted alkylene groups andC₁₋₅ alkylene groups and/or C₁₋₅ substituted alkylene groups are linkedwith any of amide bond, ether bond, urethane bond, urea bond, and esterbond; and particularly has a structure in which a plurality of singlebonds, C₁₋₃ alkylene group, C₁₋₃ substituted alkylene group, and C₁₋₃alkylene group and/or C₁₋₃ substituted alkylene groups are linked withany of amide bond, ether bond, urethane bond, urea bond, and ester bond.

Examples of the substituent group possibly bound to the linking grouprepresented by R²¹² includes group of monovalent non-metallic atomsexcluding hydrogen atom, wherein examples of which include halogen atom(—F, —Br, —Cl, —I), hydroxy group, cyano group, alkoxy group, aryloxygroup, mercapto group, alkylthio group, arylthio group, alkylcarbonylgroup, arylcarbonyl group, carboxyl group and its conjugate base group,alkoxy carbonyl group, aryloxy carbonyl group, carbamoyl group, arylgroup, alkenyl group, and alkynyl group.

R²¹³ is preferably a hydrogen atom or C₁₋₅ hydrocarbon group, morepreferably a hydrogen atom or C₁₋₃ hydrocarbon group, and particularly ahydrogen atom or methyl group.

n₂₁₁ is preferably 1 to 3, more preferably 1 or 2, and particularly 1.

Ratio of the content (mol %) of the polymerizable component havingcarboxylate group, relative to the total polymerizable components of the(meth)acrylic polymer is preferably 1 to 70% from the viewpoint ofdevelopability, more preferably 1 to 50% considering a good balancebetween the developability and printing durability, and particularly 1to 30%.

It is preferable for the (meth)acrylic polymer used in the presentinvention to additionally have a crosslinkable group. The crosslinkablegroup herein means a group capable of crosslinking the binder (D), inthe process of radical polymerization reaction which proceeds in thephotosensitive layer, when the lithographic printing plate precursor isexposed to light. While the functional group is not specifically limitedso long as it can exhibit the above-described function, examples of thefunctional group capable of proceeding addition polymerization reactioninclude ethylenic unsaturated binding group, amino group, and epoxygroup. The functional group may also be a functional group capable ofproducing a radical upon being exposed to light, and this sort ofcrosslinkable group is exemplified by thiol group and halogen group.Among them, ethylenic unsaturated binding group is preferable. Theethylenic unsaturated binding group is preferably styryl group,(meth)acryloyl group, or allyl group.

The binder (D) cures in such a way that a free radical (polymerizationinitiating radical, or propagating radical in the process ofpolymerization of radical or polymerizable compound) attaches to thecrosslinkable functional group, and crosslinkage is formed among thepolymer molecules thereof, by addition polymerization which proceedsdirectly among the polymer molecules or by sequential polymerization ofthe polymerizable compounds. Alternatively, the binder cures in such away that atoms (for example, hydrogen atoms on carbon atoms adjacent tothe functional crosslinking groups) in the polymer are abstracted byfree radicals to produce polymer radicals, and the resultant polymerradicals then combine with each other to produce the crosslinkages amongthe polymer molecules.

The content of the crosslinkable group in the (meth)acrylic polymer(content of radical polymerizable unsaturated double bond determined byiodometry) is preferably 0.01 to 10.0 mmol per one gram of the binder(D), more preferably 0.05 to 9.0 mmol, and particularly 0.1 to 8.0 mmol.

Besides the above-described repeating unit having an acid group, and thepolymerization unit having a crosslinkable group, the (meth)acrylicpolymer used in the present invention may have a polymerization unit ofalkyl (meth)acrylate or aralkyl (meth)acrylate, polymerization unit of(meth)acrylamide or its derivative, polymerization unit ofα-hydroxymethyl acrylate, or polymerization unit of styrene derivative.The alkyl group of alkyl (meth)acrylate is preferably a C₁₋₅ alkylgroup, or an alkyl group having the above-described C₂₋₈ substituentgroup, and more preferably methyl group. The aralkyl (meth)acrylate isexemplified by benzyl (meth)acrylate. The (meth)acrylamide derivative isexemplified by N-isopropylacrylamide, N-phenylmethacrylamide,N-(4-methoxycarbonylphenyl)methacrylamide, N,N-dimethylacrylamide, andmorpholinoacrylamide. The α-Hydroxymethyl acrylate is exemplified byethyl α-hydroxymethyl acrylate, and cyclohexyl α-hydroxymethyl acrylate.The styrene derivative is exemplified by styrene, and4-tert-butylstyrene.

For the case where the lithographic printing plate precursor is intendedfor on-machine development, the binder (D) preferably has a hydrophilicgroup. The hydrophilic group contributes to impart on-pressdevelopability to the photo sensitive layer. In particular, by allowingthe crosslinkable group and the hydrophilic group to coexist, theprinting durability and the on-press developability may be compatible.

Examples of the hydrophilic group possibly bound to the binder (D)include hydroxy group, carboxyl group, alkylene oxide structure, aminogroup, ammonium group, amide group, sulfo group, and phosphate group.Among them, the alkylene oxide structure having 1 to 9 C₂₋₃alkyleneoxide units is preferable. The hydrophilic group may be introduced intothe binder, typically by allowing monomers having hydrophilic group tocopolymerize.

Preferable examples of the polyurethane resin include those described inparagraphs [0099] to [0210] of Japanese Laid-Open Patent Publication No.2007-187836, paragraphs [0019] to [0100] of Japanese Laid-Open PatentPublication No. 2008-276155, paragraphs [0018] to [0107] of JapaneseLaid-Open Patent Publication No. 2005-250438, and paragraphs [0021] to[0083] of Japanese Laid-Open Patent Publication No. 2005-250158.

Preferable examples of the polyvinyl butyral resin include thosedescribed in paragraphs [0006] to [0013] of Japanese Laid-Open PatentPublication No. 2001-75279.

The binder (D) may be neutralized by a basic compound at a part of theacid groups. The basic compound is exemplified by compounds having basicnitrogen atom, alkali metal hydroxide, and quaternary ammonium salt ofalkali metal.

The binder (D) preferably has a mass average molecular weight of 5,000or larger, more preferably 10,000 to 300,000, and preferably has anumber average molecular weight of 1,000 or larger, and more preferably2000 to 250,000. The polydispersibility (mass average molecularweight/number average molecular weight) is preferably 1.1 to 10.

The binder (D) may be used alone or in combination of two or morespecies.

The content of the binder (D) is preferably 5 to 75% by mass of thetotal solid content of the photo sensitive layer, from the viewpoint ofsatisfactory levels of strength in the image-forming area and imageformability, and more preferably 10 to 70% by mass, and still morepreferably 10 to 60% by mass.

Total content of the polymerizable compound (C) and the binder (D)relative to the total solid content of the photo sensitive layer ispreferably 90% by mass or less. The content exceeding 90% by mass mayresult in degraded sensitivity and developability. The content is morepreferably 35 to 80% by mass.

(E) Sensitizing Dye

The photo sensitive layer preferably contains a dye. The dye ispreferably a sensitizing dye(E).

The sensitizing dye used for the image recording layer of thelithographic printing plate precursor according to the present inventionmay be arbitrarily selected without special limitation, so long as itcan go into an excited state upon absorption of light in the process ofpattern-wise exposure, and can supply energy to the polymerizationinitiator typically by electron transfer, energy transfer or heatgeneration, so as to improve the polymerization initiating property. Inparticular, sensitizing dyes showing maximum absorption in thewavelength range from 350 to 450 nm are preferably used.

The sensitizing dyes showing maximum absorption in the wavelength rangefrom 350 to 450 nm include merocyanines, benzopyranes, coumarines,aromatic ketones, anthracenes, styryls, and oxazoles.

Among the sensitizing dyes showing maximum absorption in the wavelengthrange from 350 to 450 nm, preferable dyes are those represented by theformula (IX), from the viewpoint of large sensitivity.

In the formula (IX), A²²¹ represents an aryl group or heteroaryl groupwhich may have a substituent group, and X²²¹ represents an oxygen atom,sulfur atom or ═N(R²²³). Each of R²²¹, R²²² and R²²³ independentlyrepresents a monovalent group of non-metallic atom, wherein A²²¹ andR²²¹, or R²²² and R²²³, may combine respectively to form an aliphatic oraromatic ring.

The formula (IX) will now be further detailed. The monovalent group ofnon-metallic atom represented by R²²¹, R²²² or R²²³ is preferably ahydrogen atom, substituted or unsubstituted alkyl group, substituted orunsubstituted alkenyl group, substituted or unsubstituted aryl group,substituted or unsubstituted heteroaryl group, substituted orunsubstituted alkoxy group, substituted or unsubstituted alkylthiogroup, hydroxy group, and halogen atom.

The aryl group and heteroaryl group represented by A²²¹, which may havea substituent group, are same as the substituted or unsubstituted arylgroup, and substituted or unsubstituted heteroaryl group representedrespectively by R²²¹, R²²² and R²²³.

Specific examples of the sensitizing dye preferably used herein includethe compounds described in paragraphs [0047] to [0053] of JapaneseLaid-Open Patent Publication No. 2007-58170, paragraphs [0036] to [0037]of Japanese Laid-Open Patent Publication No. 2007-93866, and paragraphs[0042] to [0047] of Japanese Laid-Open Patent Publication No.2007-72816.

Also the sensitizing dyes described in Japanese Laid-Open PatentPublication Nos. 2006-189604, 2007-171406, 2007-206216, 2007-206217,2007-225701, 2007-225702, 2007-316582, and 2007-328243 are preferablyused.

Next, the sensitizing dye showing maximum absorption in the wavelengthrange from 750 to 1400 nm (also referred to as “infrared absorber”,hereinafter) will be described. The infrared absorber preferably usedherein is dye or pigment.

The dye adoptable herein may be arbitrarily selected from commerciallyavailable dyes and those described in literatures such as “Senryo Binran(Dye Handbook)” (edited by The Society of Synthetic Organic Chemistry,Japan, 1970). The specific examples include azo dye, metal complex azodye, pyrazolone azo dye, naphthoquinone dye, anthraquinone dye,phthalocyanine dye, carbonium dye, quinone imine dye, methine dye,cyanine dye, squarylium colorant, pyrylium salt dye, and metal thiolatecomplex dye.

Among them, particularly preferable examples include cyanine colorant,squarylium colorant, pyrylium salt, nickel thiolate complex, andindolenine cyanine colorant. More preferable examples include cyaninecolorant and indolenine cyanine colorant, and particularly preferableexample include a cyanine colorant represented by the formula (a) below:

In the formula (a), X¹³¹ represents a hydrogen atom, halogen atom,—NPh₂, —X¹³²-L¹³¹ or the group shown below, where

In the formula, X¹³² represents an oxygen atom, nitrogen atom or sulfuratom, and L¹³¹ represents a C₁₋₁₂ hydrocarbon group, aryl group having ahetero atom (N, S, O, halogen, Se), and C₁₋₁₂ hydrocarbon group having ahetero atom. X_(a) ⁻ is synonymous with Z_(a) ⁻ described later. R¹⁴¹represents a substituent group selected from hydrogen atom or alkylgroup, aryl group, substituted or unsubstituted amino group, and halogenatom.

Each of R¹³¹ and R¹³² independently represents C₁₋₁₂ hydrocarbon group.From the viewpoint of stability of coating liquid for forming the photosensitive layer, each of R¹³¹ and R¹³² is preferably a C₂ or longerhydrocarbon group. R¹³¹ and R¹³² may combine with each other to form aring which is preferably a five-membered ring or six-membered ring.

Ar¹³¹ and Ar¹³² may be same or different, and each represents an arylgroup which may have a substituent group. Preferable examples of thearyl group include benzene ring group and naphthalene ring group.Preferable examples of the substituent group include C₁₂ or shorterhydrocarbon group, halogen atom, and C12 or shorter alkoxy group. Y¹³¹and Y¹³² may be same or different, and each represents a sulfur atom orC₁₂ or shorter dialkylmethylene group. R¹³³ and R¹³⁴ may be same ordifferent, and each represents a C₂₀ or shorter hydrocarbon group whichmay have a substituent group. Preferable examples of the substituentgroup include a C₁₂ or shorter alkoxy group, carboxyl group, and sulfogroup. R¹³⁵, R¹³⁶, R¹³⁷ and R¹³⁸ may be same or different, and eachrepresents a hydrogen atom or C₁₂ or shorter hydrocarbon group. From theviewpoint of availability of the source materials, hydrogen atom ispreferable. Z_(a) ⁻ represents a counter anion. Note that Z_(a) ⁻ is notnecessary if the cyanine colorant represented by the formula (a) has ananionic substituent group in the structure thereof, and is omissible ifthere is no need of neutralization of electric charge. Preferableexamples of Z_(a) ⁻ include halide ion, perchlorate ion,tetrafluoroborate ion, hexafluorophosphate ion and sulfonate ion fromthe viewpoint of storage stability of coating liquid for forming thephoto sensitive layer. Particularly preferable examples includeperchlorate ion, hexafluorophosphate ion and aryl sulfonate ion.

Specific examples of the cyanine colorant represented by the formula (a)include the compounds described in paragraphs [0017] to [0019] ofJapanese Laid-Open Patent Publication No. 2001-133969, paragraphs [0016]to [0021] of Japanese Laid-Open Patent Publication No. 2002-023360, andparagraphs [0012] to [0037] of Japanese Laid-Open Patent Publication No.2002-040638, preferable examples include those described in paragraphs[0034] to [0041] of Japanese Laid-Open Patent Publication No.2002-278057, and paragraphs [0080] to [0086] of Japanese Laid-OpenPatent Publication No. 2008-195018, and particularly preferable examplesinclude those described in paragraphs [0035] to [0043] of JapaneseLaid-Open Patent Publication No. 2007-90850.

Also compounds described in paragraphs [0008] to [0009] of JapaneseLaid-Open Patent Publication No. H05-5005, and paragraphs [0022] to[0025] of Japanese Laid-Open Patent Publication No. 2001-222101 arepreferably used.

The infrared absorbing dye may be used alone, or in combination of twoor more species, and may contain an infrared absorber other thaninfrared absorbing dye, which is exemplified by pigment. As the pigment,the compounds described in paragraphs [0072] to [0076] of JapaneseLaid-Open Patent Publication No. 2008-195018 are preferable.

The content of the sensitizing dye (E) is preferably 0.05 to 30 parts bymass relative to the total solid content (100 parts by mass) of thephoto sensitive layer, more preferably 0.1 to 20 parts by mass, andparticularly 0.2 to 10 parts by mass.

(F) Low-Molecular-Weight Hydrophilic Compound

The photo sensitive layer may contain a low-molecular-weight hydrophiliccompound, for the purpose of improving the on-press developabilitywithout degrading the printing durability.

Examples of the low-molecular-weight hydrophilic compound, categorizedas water-soluble organic compound, include glycols such as ethyleneglycol, diethylene glycol, triethylene glycol, propylene glycol,dipropylene glycol, and tripropylene glycol, and ether or esterderivatives thereof; polyols such as glycerin, pentaerythritol, andtris(2-hydroxyethyl) isocyanurate; organic amines such astriethanolamine, diethanolamine, and monoethanolamine, and saltsthereof; organic sulfonic acids such as alkyl sulfonic acid,toluenesulfonic acid, and benzenesulfonic acid, and salts thereof;organic sulfamic acids such as alkyl sulfamic acid, and salt thereof;organic sulfuric acids such as alkyl sulfuric acid, alkyl ether sulfuricacid, and salts thereof; organic phosphonic acids such asphenylphosphonic acid, and salt thereof; organic carboxylic acids suchas tartaric acid, oxalic acid, citric acid, malic acid, lactic acid,gluconic acid, and amino acid, and salts thereof; and betaines.

Among them, at least one species selected from polyols, organic sulfatesalts, organic sulfonate salts, and betaines are preferably contained inthe present invention.

Specific examples of the organic sulfonate salt include alkylsulfonatesalt such as sodium-butylsulfonate, sodium n-hexylsulfonate, sodium2-ethylhexylsulfonate, sodium cyclohexylsulfonate, and sodiumn-octylsulfonate; alkylsulfonate salt having an ethylene oxide chainsuch as sodium 5,8,11-trioxapentadecane-1-sulfonate, sodium5,8,11-trioxaheptadecane-1-sulfonate, sodium13-ethyl-5,8,11-trioxaheptadecane-1-sulfonate, and sodium5,8,11,14-tetraoxatetracosane-1-sulfonate; aryl sulfonate salt such assodium benzenesulfonate, sodium p-toluenesulfonate, sodiump-hydroxybenzenesulfonate, sodium p-styrenesulfonate, sodium dimethylisophthalate-5-sulfonate, sodium 1-naphthylsulfonate, sodium4-hydroxynaphthylsulfonate, disodium 1,5-naphthalenedisulfonate, andtrisodium 1,3,6-naphthalenetrisulfonate; the compounds described inparagraphs [0026] to [0031] of Japanese Laid-Open Patent Publication No.2007-276454, and paragraphs [0020] to [0047] of Japanese Laid-OpenPatent Publication No. 2009-154525. The salt may also be potassium saltsor lithium salts.

The organic sulfate salts are exemplified by sulfate salts of alkyl,alkenyl, alkynyl, aryl or heterocyclic monoether of polyethylene oxide.The number of ethylene oxide unit is preferably 1 to 4, and the saltsare preferably sodium salt, potassium salt or lithium salt. Specificexamples thereof include the compounds described in paragraphs [0034] to[0038] of Japanese Laid-Open Patent Publication No. 2007-276454.

The betaine is preferably a compound having C₁₋₅ hydrocarbon substituentgroup on the nitrogen atom, and preferable examples includetrimethylammonium acetate, dimethylpropylammonium acetate,3-hydroxy-4-trimethylammoniobutyrate, 4-(1-pyridinio)butyrate,1-hydroxyethyl-1-imidazolio acetate, trimethylammonium methanesulfonate,dimethylpropylammonium methanesulfonate,3-trimethylammonio-1-propanesulfonate, and3-(1-pyridinio)-1-propanesulfonate.

The low-molecular-weight hydrophilic compound scarcely exhibits asurfactant activity due to its small size of the hydrophobic portion, sothat fountain solution does not immerse into the exposed area of thephoto sensitive layer (image-forming area) to consequently degrade thehydrophobicity and film strength of the image-forming area, and therebythe ink receptivity and printing durability of the image recording layerare kept at desirable levels.

The content of the low-molecular-weight hydrophilic compound in thephoto sensitive layer is preferably 0.5 to 20% by mass of the totalsolid content of the photo sensitive layer, more preferably 1 to 15% bymass, and more preferably 2 to 10% by mass. In this range, desirablelevels of on-press developability and printing durability are obtained.The low-molecular-weight hydrophilic compound may be used alone, or incombination of two or more species.

(G) Sensitizer

The image recording layer may contain a sensitizer such as phosphoniumcompound, nitrogen-containing low-molecular-weight compound, andammonium group-containing polymer, aiming at improving inkingperformance. In particular, for the case where the protective layercontains an inorganic layered compound, the sensitizer functions as asurface coating agent of the inorganic layered compound, and prevent theinking performance from degrading in the process of printing, due to theinorganic layered compound.

Preferable examples of the phosphonium compound include those describedin Japanese Laid-Open Patent Publication Nos. 2006-297907 and2007-50660. Specific examples thereof include tetrabutylphosphoniumiodide, butyltriphenylphosphonium bromide, tetraphenylphosphoniumbromide, 1,4-bis(triphenylphosphonio)butane di(hexafluorophosphate),1,7-bis(triphenylphosphonio)heptane sulfate, and1,9-bis(triphenylphosphonio)nonanenaphthalene-2,7-disulfonate.

The nitrogen-containing low-molecular-weight compound is exemplified byamine salts, and quaternary ammonium salts. Other examples includeimidazolinium salts, benzoimidazolinium salts, pyrydinium salts, andquinolinium salts. Among them, quaternary ammonium salts and pyrydiniumsalts are preferable. Specific examples include tetramethylammoniumhexafluorophosphate, tetrabutylammonium hexafluorophosphate,dodecyltrimethylammonium p-toluenesulfonate, benzyl triethylammoniumhexafluorophosphate, benzyl dimethyloctylammonium hexafluorophosphate,benzyl dimethyldodecylammonium hexafluorophosphate, the compoundsdescribed in paragraphs [0021] to [0037] of Japanese Laid-Open PatentPublication No. 2008-284858, and the compounds described in paragraphs[0030] to [0057] of Japanese Laid-Open Patent Publication No.2009-90645.

While the ammonium group-containing polymer may be arbitrarily selectedso long as it has an ammonium group in the structure thereof, apreferable polymer contains, as a copolymerizable component, 5 to 80 mol% of (meth)acrylate having an ammonium group in the side chain thereof.Specific examples include the polymers described in paragraphs [0089] to[0105] of Japanese Laid-Open Patent Publication No. 2009-208458.

The ammonium salt-containing polymer preferably has a reduced specificviscosity (in ml/g), measured by the method of measurement describedbelow, of 5 to 120, more preferably 10 to 110, and particularly 15 to100. Mass average molecular weight, converted from the reduced specificviscosity, is preferably 10,000 to 150,000, more preferably 17,000 to140,000, and particularly 20,000 to 130,000.

<<Method of Measuring Reduced Specific Viscosity>>

In a 20-ml measuring flask, 3.33 g (1 g as solid content) of a 30%polymer solution is weighed, and the flask is filled up withN-methylpyrrolidone. The obtained solution is allowed to stand in athermostat chamber at 30° C. for 30 minutes, and then placed in aUbbelohde reduced viscosity tube (viscometer constant=0.010 cSt/s), andthe time it takes for the solution to elute at 30° C. is measured. Themeasurement is repeated twice using the same sample, to thereby find anaverage value. The blank (N-methylpyrrolidone only) is also measuredsimilarly, and the reduced specific viscosity (ml/g) is calculated bythe formula below.

${{Reduced}\mspace{14mu} {specific}\mspace{14mu} {viscosity}\mspace{14mu} \left( {{ml}\text{/}g} \right)} = \frac{\frac{\begin{matrix}{{{Elution}\mspace{14mu} {time}\mspace{14mu} {of}\mspace{14mu} {sample}\mspace{14mu} {solution}\mspace{14mu} \left( \sec \right)} -} \\{{Elution}\mspace{14mu} {time}\mspace{14mu} {of}\mspace{14mu} {blank}\mspace{14mu} \left( \sec \right)}\end{matrix}}{{Elution}\mspace{14mu} {time}\mspace{14mu} {of}\mspace{14mu} {blank}\mspace{14mu} \left( \sec \right)}}{\frac{3.33\mspace{14mu} (g) \times \frac{30}{100}}{20\mspace{14mu} ({ml})}}$

Specific examples of the ammonium group-containing polymer will beenumerated below:

-   (1) 2-(trimethylammonio)ethyl methacrylate    p-toluenesulfonate/3,6-dioxaheptyl methacrylate copolymer (molar    ratio=10/90, mass average molecular weight; 450,000)-   (2) 2-(trimethylammonio)ethyl methacrylate    hexafluorophosphate/3,6-dioxaheptyl methacrylate copolymer (molar    ratio=20/80, mass average molecular weight: 600,000)-   (3) 2-(ethyldimethylammonio)ethyl methacrylate    p-toluenesulfonate/hexyl methacrylate copolymer (molar ratio=30/70,    mass average molecular weight: 450,000)-   (4) 2-(trimethylammonio)ethyl methacrylate    hexafluorophosphate/2-ethylhexyl methacrylate copolymer (molar    ratio=20/80, mass average molecular weight: 600,000)-   (5) 2-(trimethylammonio)ethyl methacrylate methylsulfate/hexyl    methacrylate copolymer (molar ratio=40/60, mass average molecular    weight: 700,000)-   (6) 2-(butyldimethylammonio)ethyl methacrylate    hexafluorophosphate/3,6-dioxaheptyl methacrylate copolymer (molar    ratio=25/75 mass average molecular weight: 650,000)-   (7) 2-(butyldimethylammonio)ethyl acrylate    hexafluorophosphate/3,6-dioxaheptyl methacrylate copolymer (molar    ratio=20/80, mass average molecular weight: 650,000)-   (8) 2-(butyldimethylammonio)ethyl methacrylate    13-ethyl-5,8,11-trioxa-1-heptadecane sulfonate/3,6-dioxaheptyl    methacrylate copolymer (molar ratio=20/80, mass average molecular    weight: 750,000)-   (9) 2-(butyldimethylammonio)ethyl methacrylate    hexafluorophosphate/3,6-dioxaheptyl methacrylate    /2-hydroxy-3-methacryloyloxypropyl methacrylate copolymer (molar    ratio=15/80/5 mass average molecular weight: 650,000)

The content of the sensitizer is preferably 0.01 to 30.0% by mass of thetotal solid content of the photo sensitive layer, more preferably 0.01to 15.0% by mass, and still more preferably 1 to 5% by mass.

(H) Hydrophobization Precursor

The image recording layer may contain a hydrophobization precursor, forthe purpose of improving the on-press developability. Thehydrophobization precursor means a fine particle capable of turning,upon heating, the image recording layer into hydrophobic. The fineparticle is preferably at least one species selected from hydrophobicthermoplastic polymer particle, thermoreactive polymer particle, polymerparticle having polymerizable group, and microcapsule and microgel(crosslinked polymer particle) containing hydrophobic compound. Amongthem, polymer particle and microgel having polymerizable group arepreferable.

Preferable examples of the hydrophobic thermoplastic polymer particleinclude those described in Research Disclosure No. 333003 published inJanuary 1992, Japanese Laid-Open Patent Publication Nos. H09-123387,H09-131850, H09-171249, H09-171250 and European Patent No. 931647.

Specific examples of polymer composing the polymer particle includeethylene, styrene, vinyl chloride, methyl acrylate, ethyl acrylate,methyl methacrylate, ethyl methacrylate, vinylidene chloride,acrylonitrile, vinylcarbazole, acrylate or methacrylate having apolyalkylene structure, all of which being available in the form ofmonomer, homopolymer, copolymer and mixture. Among them, more preferableexamples include polystyrene, copolymer containing styrene andacrylonitrile, and methyl polymethacrylate.

Average particle size of the hydrophobic thermoplastic polymer particleused in the present invention is preferably 0.01 to 2.0 μm.

The thermoreactive polymer particle used in the present invention isexemplified by polymer particle having a thermoreactive group whichforms a hydrophobic domain as a result of crosslinking by thermalreaction and concomitant change in the functional group.

While the thermoreactive group contained in the polymer particle used inthe present invention may be arbitrarily selected from those capable ofproceeding any type of reaction so long as it can form a chemical bond,it is preferably a polymerizable group. The preferable examples includeethylenic unsaturated group which undergoes radical polymerizationreaction (acryloyl group, methacryloyl group, vinyl group, allyl group,etc.); cation polymerizable group (vinyl group, vinyloxy group, epoxygroup, oxetanyl group, etc.); isocyanate group or block thereof whichundergoes addition reaction; epoxy group, vinyloxy group and functionalgroup containing an activated hydrogen atom reactive with them (aminogroup, hydroxy group, carboxyl group, etc.); carboxyl group whichundergoes condensation reaction, and functional group capable ofreacting therewith and having a hydroxy group or amino group; and acidanhydride which undergoes ring-opening addition reaction, and aminogroup or hydroxy group allow to react therewith.

The microcapsule used in the present invention contains all of, or apart of, the constituents of the photo sensitive layer, typically asdescribed in Japanese Laid-Open Patent Publication Nos. 2001-277740 and2001-277742. The constituents of the image recording layer may also becontained outside the microcapsule. Still alternatively, the photosensitive layer containing microcapsule may be configured so as tocontain the hydrophobic constituents encapsulated in the microcapsule,and hydrophilic constituents outside the microcapsule.

The microgel used in the present invention may contain at least eithertherein or on the surface thereof, a part of constituents of the photosensitive layer. In particular, an embodiment of reactive microgel,configured by attaching the radical-polymerizable group onto the surfacethereof, is preferable from the viewpoint of image-forming sensitivityand printing durability.

Encapsulation of the constituents of the photo sensitive layer into themicrocapsule or microgel is arbitrarily selectable from those known inthe art.

Average particle size of the microcapsule or microgel is preferably 0.01to 3.0 μm, more preferably 0.05 to 2.0 μm, and particularly 0.10 to 1.0μm. Satisfactory levels of resolution and long-term stability may beensured in the above-described ranges.

The content of the hydrophobization precursor is preferably 5 to 90% bymass relative to the total solid content of the photo sensitive layer.

(I) Other Components of Image Recording Layer

The photo sensitive layer preferably contains chain transfer agent. Thechain transfer agent is defined typically in “Kobunshi Jiten (TheDictionary of Polymer), 3rd Edition” (edited by The Society of PolymerScience, Japan, 2005) p. 683-684. The chain transfer agent adoptableherein includes compound having SH, PH, SiH or GeH in the moleculethereof. These groups may produce a radical by donating a hydrogen to alow-active radical species, or, may produce a radical after beingoxidized, followed by deprotonation. It is particularly preferable forthe photo sensitive layer to contain a thiol compound (2-mercaptobenzimidazoles, 2-mercapto benzthiazoles, 2-mercapto benzoxazoles,3-mercapto triazoles, 5-mercapto tetrazoles, etc.).

The content of the chain transfer agent is preferably 0.01 to 20 partsby mass relative to the total solid content (100 parts by mass) of thephoto sensitive layer, more preferably 1 to 10 parts by mass, andparticularly 1 to 5 parts by mass.

The photo sensitive layer may further contain various additives asneeded. The additives are exemplified by surfactant for enhancingdevelopability and improving coating surface texture; hydrophilicpolymer for improving developability and dispersion stability of themicrocapsule; colorant and baking agent for easy discrimination betweenthe image-forming area and the non-image-forming area; polymerizationinhibitor for avoiding unnecessary thermal polymerization of thepolymerizable compound in the process of manufacturing or storage of thephoto sensitive layer; hydrophobic low-molecular-weight compound such ashigher aliphatic acid derivative for avoiding inhibition ofoxygen-induced polymerization; inorganic particle and organic particlefor improving strength of cured film in the image-forming area;co-sensitizer for improving the sensitivity; and plasticizer forimproving plasticity. These compounds may be any of those known in theart, such as those disclosed in paragraphs [0161] to [0215] of JapaneseLaid-Open Patent Publication No. 2007-206217, paragraph [0067] ofPublished Japanese Translation of PCT International Publication forPatent Application No. 2005-509192, and paragraphs [0023] to [0026], and[0059] to [0066] of Japanese Laid-Open Patent Publication No.2004-310000. The surfactant may also be those which may be added to thedeveloper described later.

(Formation of Photo Sensitive Layer)

The photo sensitive layer in the lithographic printing plate precursoraccording to the present invention may be formed by an arbitrary methodknown in the art, without special limitation. The photo sensitive layeris formed by dispersing or dissolving the above-described necessarycomponents of the photo sensitive layer into a solvent to prepare acoating liquid, and then coating the liquid. The solvent adoptableherein is exemplified by methyl ethyl ketone, ethylene glycol monomethylether, 1-methoxy-2-propanol, 2-methoxyethyl acetate, 1-methoxy-2-propylacetate, and γ-butyrolactone, but not limited thereto. The solvent maybe used alone, or in combination of two or more species. The solidcontent of the coating liquid is preferably 1 to 50% by mass.

The amount of coating (solid content) of the photo sensitive layer ispreferably 0.3 to 3.0 g/m². Method of coating may be arbitrarilyselected from various methods, including bar coater coating, spincoating, spray coating, curtain coating, dip coating, air knife coating,blade coating, and roll coating.

The copolymer (A) may be incorporated into the photo sensitive layer orundercoat layer, by adding the copolymer (A) to the coating liquid forforming the photo sensitive layer, or to the coating liquid for formingthe undercoat layer. For the case where the copolymer (A) is containedin the photo sensitive layer, the content of the copolymer (A) (solidcontent) is preferably 0.1 to 100 mg/m², more preferably 1 to 30 mg/m²,and still more preferably 5 to 24 mg/m².

[Support]

The support used for the lithographic printing plate precursor accordingto the present invention is not specifically limited, provided that itis plate-like hydrophilic support with dimensional stability. Aluminumplate is particularly preferable as the support. The aluminum platepreferably undergoes surface treatment such as roughening or anodizingprior to use. The surface of aluminum plate may be roughened by variousmethods including mechanical roughening, electro-chemical roughening(eroding the surface by an electro-chemical process), and chemicalroughening (selectively eroding the surface in a chemical process).Preferable examples of these methods of treatment are descried inparagraphs [0241] to [0245] of Japanese Laid-Open Patent Publication No.2007-206217.

The support preferably has a center line average roughness of 0.10 to1.2 μm. In this range, the support will exhibit good adhesiveness withthe photo sensitive layer, good printing durability, and good stainingresistance.

Color density of the support is preferably 0.15 to 0.65 in terms ofreflection density value. In this range, good image forming performanceby virtue of suppressed halation in the process of pattern-wiseexposure, and readiness of plate check after development may be ensured.

The support is preferably 0.1 to 0.6 mm thick, more preferably 0.15 to0.4 mm thick, and still more preferably 0.2 to 0.3 mm thick.

<Hydrophilization>

In the lithographic printing plate precursor according to the presentinvention, it is also effective to hydrophilize the surface of thesupport, for the purpose of improving the hydrophilicity in thenon-image-forming area and of preventing printing blot.

Methods of hydrophilization of the surface of the support include alkalimetal silicate treatment by which the support is dipped into an aqueoussolution of sodium silicate or the like, for electrolytic treatment;treatment using potassium fluorozirconate; and treatment using polyvinylphosphonate. The method using an aqueous solution of polyvinylphosphonate is preferably used.

[Extra Layer Optionally Provided Between the Substrate and thePhotosensitive Layer]

In the lithographic printing plate precursor of the present invention, aprimer layer is conveniently provided between the substrate and thephotosensitive layer to improve hydrophilicity of non-image areas and toprevent print staining.

<Primer Layer>

When the lithographic printing plate precursor of the present inventionhas a primer layer, the primer layer preferably contains the copolymer(A). In this case, the content of the copolymer (A) is as described forthe content of the copolymer (A) in the photosensitive layer. The primerlayer may further contain additional compounds other than the copolymer(A), and such additional compounds preferably include the silanecoupling agents containing an addition-polymerizable ethylenic doublebond-reactive group described in JP-A-H10-282679, the phosphoruscompounds containing an ethylenic double bond-reactive group describedin JP-A-H2-304441 and the like. Especially preferred compounds arecompounds having a polymerizable group such as methacryl, allyl and thelike and a substrate-adsorbing group such as sulfonic acid, phosphoricacid, phosphoric acid ester and the like. Other preferred compoundsinclude compounds containing a hydrophilicity-conferring group such asethylene oxide and the like in addition to the polymerizable group andsubstrate-adsorbing group.The primer layer can be provided by applying a solution of the compounddissolved in water or an organic solvent such as methanol, ethanol,methyl ethyl ketone or the like or a mixed solvent thereof on thesubstrate and drying it, or immersing the substrate in a solution of thecompound dissolved in water or an organic solvent such as methanol,ethanol, methyl ethyl ketone or the like or a mixed solvent thereof toallow the compound to be adsorbed, and then washing it with water or thelike and drying it. In the former method, a solution of the compound ata concentration of 0.005 to 10% by mass can be applied by varioustechniques. Any technique can be used, such as bar coating, spincoating, spray coating, curtain coating and the like, for example. Inthe latter method, the concentration of the solution is 0.01 to 20% bymass, preferably 0.05 to 5% by mass, the immersion temperature is 20 to90° C., preferably 25 to 50° C., and the immersion time is 0.1 second to20 minutes, preferably 2 seconds to 1 minute.The coating mass of the primer layer (expressed as solids) is preferably0.1 to 100 mg/m², more preferably 1 to 30 mg/m².

[Protective Layer]

For the purpose of blocking diffusive intrusion of oxygen which mayinhibit the polymerization reaction in the process of exposure to light,the lithographic printing plate precursor according to the presentinvention is preferably provided with the protective layer (oxygenbarrier layer) on the photo sensitive layer. Materials for composing theprotective layer are arbitrarily selectable either from water-solublepolymer and water-insoluble polymer, and two or more species may becombined as necessary. More specifically, polyvinyl alcohol, modifiedpolyvinyl alcohol, polyvinyl pyrrolidone, water-soluble cellulosederivative, and poly(meth)acrylonitrile are exemplified. Among them,water-soluble polymer compound is preferably used by virtue of itsrelatively good crystallinity. More specifically, a good result may beobtained by using polyvinyl alcohol as a major constituent, from theviewpoint of achieving excellent basic performances such as oxygenbarrier performance, and removability in development.

Polyvinyl alcohol used for the protective layer may partially besubstituted, at the hydroxy groups thereof, by ester, ether or acetal,so long as a certain amount of unsubstituted vinyl alcohol units,necessary for ensuring oxygen barrier performance and water-solubility,is contained. Similarly, polyvinyl alcohol may also contain otherpolymerizable component partially in the structure thereof. Polyvinylalcohol may be obtained by hydrolyzing polyvinyl acetate. Specificexamples of polyvinyl alcohol include those having a degree ofhydrolysis of 69.0 to 100 mol %, and having a number of polymerizablerepeating units of 300 to 2400. More specific examples include PVA-102,PVA-103, PVA-105, PVA-110, PVA-117, PVA-117H, PVA-120, PVA-124,PVA-124H, PVA-CS, PVA-CST, PVA-HC, PVA-203, PVA-204, PVA-205, PVA-210,PVA-217, PVA-220, PVA-224, PVA-235, PVA-217EE, PVA-217E, PVA-220E,PVA-224E, PVA-403, PVA-405, PVA-420, PVA-424H, PVA-505, PVA-617,PVA-613, PVA-706 and PVA L-8, all of which commercially available fromKuraray Co. Ltd. Polyvinyl alcohol may be used alone, or in the form ofmixture. The content of polyvinyl alcohol in the protective layer ispreferably 20 to 95% by mass, and more preferably 30 to 90% by mass.

Also modified polyvinyl alcohol may preferably be used. In particular,acid-modified polyvinyl alcohol having the carboxylate group orsulfonate group is preferably used. More specifically, preferableexamples include the polyvinyl alcohol described in Japanese Laid-OpenPatent Publication Nos. 2005-250216 and 2006-259137.

For the case where polyvinyl alcohol is used in a mixed form with othermaterials, the materials to be mixed are preferably modified polyvinylalcohol, polyvinyl pyrrolidone or a modified product thereof, from theviewpoint of oxygen barrier performance and readiness of removal indevelopment. The content in the protective layer is 3.5 to 80% by mass,preferably 10 to 60% by mass, and more preferably 15 to 30% by mass.

The protective layer may be added with several percents, relative to thepolymer, of glycerin, dipropylene glycol or the like so as to giveflexibility. Alternatively, several percents by mass, relative to thepolymer, of anionic surfactants such as the sodium alkyl sulfuric acidand sodium alkyl sulfonate; ampholytic surfactants such as alkylaminocarboxylate salt, and alkylamino dicarboxylate salt; and nonionicsurfactants such as polyoxyethylene alkyl phenyl ether polymer may beadded.

In addition, for the purpose of improving the oxygen barrier performanceand surface protective performance of the photo sensitive layer, theprotective layer may contain an inorganic layered compound. Among theinorganic layered compounds, fluorine-containing swellable syntheticmica, which is a synthetic inorganic layered compound, is particularlyuseful. More specifically, preferable examples include the inorganiclayered compounds described in Japanese Laid-Open Patent Publication No.2005-119273.

The amount of coating of the protective layer is preferably 0.05 to 10g/m², and is more preferably 0.1 to 5 g/m² if the inorganic layeredcompound is contained, and whereas more preferably 0.5 to 5 g/m² if theinorganic layered compound is not contained.

[Back Coat Layer]

The lithographic printing plate precursor according to the presentinvention may be provided with a back coat layer on the back surface ofthe support as necessary. The back coat layer is preferably exemplifiedby a cover layer composed of the organic polymer compounds described inJapanese Laid-Open Patent Publication No. H05-45885, or composed of themetal oxides described in Japanese Laid-Open Patent Publication No.H06-35174 which are obtained by allowing organic metal compound orinorganic metal compound to hydrolyze or undergo polycondensation. Amongthem, alkoxy compounds of silicon, such as Si(OCH₃)₄, Si(OC₂H₅)₄,Si(OC₃H₇)₄, Si(CO₄H₉)₄ are preferable in view of inexpensiveness andavailability of the source materials.

Second Embodiment Lithographic Printing Plate Precursor

The lithographic printing plate precursor of the present inventioncomprises a substrate; a photosensitive layer containing at least (B) apolymerization initiator; (C) a polymerizable compound and (D) a binderprovided on the substrate; and optionally an extra layer providedbetween the substrate and the photosensitive layer, wherein thephotosensitive layer or the extra layer adjacent to the substratecontains (A) a copolymer different from (D) the binder and wherein thecopolymer comprises (a0) a repeating unit having a structure representedby formula (a1-0) below in a side chain.

In formula (a1-0), L¹ represents a divalent covalent linking group,excluding alkylene. Z¹ represents a covalent linking group selected fromthe group consisting of alkylene, arylene, —O—, —S— and a combinationthereof, provided that both ends are not —O— or —S—, and when L¹ isarylene, Z¹ is not arylene. X¹ represents a hydrogen atom or anelectron-releasing group having a Hammett substituent constant op valueof 0.2 or less. The asterisk (*) indicates the point of attachment tothe main chain of the copolymer. Lithographic printing plates havingexcellent developability, handling properties, printing durability withnormal inks and printing durability with UV inks can be provided byusing the lithographic printing plate precursor of the present inventionhaving the features described above.Preferably, the lithographic printing plate precursor of the presentinvention can be directly converted into a plate using various lasersfrom digital signals of computers or the like, i.e., it is applicable toso-called computer-to-plate. Preferably, it can also be developed inaqueous solutions at pH 2.0 to 10.0 or less or on a printing press.Preferred aspects of the lithographic printing plate precursor of thepresent invention are explained in detail below.

The lithographic printing plate precursor of the present inventioncomprises a substrate and a photosensitive layer provided on thesubstrate.

Further, the lithographic printing plate precursor of the presentinvention may optionally comprise an extra layer between the substrateand the photosensitive layer. The lithographic printing plate precursorof the present invention preferably comprises a primer layer as theextra layer.Further, the lithographic printing plate precursor of the presentinvention preferably comprises a protective layer on the surface of thephotosensitive layer opposite to the substrate.Further, the lithographic printing plate precursor of the presentinvention may comprise a back coating layer on the bottom of thesubstrate as appropriate.The photosensitive layer, extra layer, protective layer, and backcoating layer constituting the lithographic printing plate precursor ofthe present invention are explained in order below, and processes forforming the lithographic printing plate precursor of the presentinvention are also explained.

Photosensitive Layer>

The photosensitive layer of the lithographic printing plate precursor ofthe present invention contains at least (B) a polymerization initiator,(C) a polymerizable compound, and (D) a binder.Further, the lithographic printing plate precursor of the presentinvention is characterized in that the photosensitive layer or the extralayer contains (A) a copolymer different from (D) the binder wherein thecopolymer comprises (a0) a repeating unit having a structure representedby formula (a1-0) above in a side chain, i.e., the photosensitive layermay contain the copolymer (A). When the primer layer described below isprovided as the extra layer between the substrate and the photosensitivelayer, the photosensitive layer may not contain the copolymer (A), butthe primer layer may contain the copolymer (A). However, the primerlayer preferably contains the copolymer (A) in the lithographic printingplate precursor of the present invention.Further, the photosensitive layer may further contain other componentsas appropriate.The components of the photosensitive layer are explained in detailbelow.

(A) Copolymer

In the lithographic printing plate precursor of the present invention,the photosensitive layer adjacent to the substrate may contain acopolymer comprising (a0) a repeating unit having a structurerepresented by formula (a1-0) below in a side chain. Although the primerlayer preferably contains the copolymer (A) in the lithographic printingplate precursor of the present invention, the copolymer (A) is describedin detail below in the photosensitive layer for sake of explanation.

In formula (a1-0), L¹ represents a divalent covalent linking group,excluding alkylene. Z¹ represents a covalent linking group selected fromthe group consisting of alkylene, arylene, —O—, —S— and a combinationthereof, provided that both ends are not —O— or —S—, and when L¹ isarylene, Z¹ is not arylene. X¹ represents a hydrogen atom or anelectron-releasing group having a Hammett substituent constant op valueof 0.2 or less. The asterisk (*) indicates the point of attachment tothe main chain of the copolymer. The structures of the repeating unitspreferably contained in the copolymer (A) and the ratios of them in thecopolymer are explained below.

(a0) Repeating unit having a structure represented by formula (a1-0) ina side chain:

First, (a0) the repeating unit having a structure represented by formula(a1-0) in a side chain is explained. In formula (a1-0) above, thedivalent covalent linking group represented by L¹ excludes alkylene. Thedivalent covalent linking group represented by L¹ is preferably adivalent linking group selected from the group consisting of —O—, —S—,—C(═O)—, —SO₂—, —NH— (wherein the hydrogen atom in —NH—may be replacedby a substituent, and typical examples of substituents include C1-10alkyl and C6-15 aryl) or arylene or any combination of these groups. Inthe present invention, L¹ is preferably a divalent linking groupselected from the group consisting of —O—, —C(═O)—, —NH—, C6-16 aryleneor a combination thereof, more preferably *—C(═O)—O—, *—C(═O)—NH—,1,2-phenylene, 1,3-phenylene, 1,4-phenylene, 1,2-naphthalene,1,5-naphthalene or the like, even more preferably *—C(═O)—O—,*—C(═O)—NH—, 1,4-phenylene or the like, especially preferably*—C(═O)—NH—. The asterisk (*) here indicates the point of attachment tothe main chain of the polymer compound, i.e., the copolymer (A).Moreover, the hydrogen atoms in these groups may be replaced bysubstituents.

In formula (a1-0) above, Z¹ represents a covalent linking group selectedfrom the group consisting of alkylene, arylene, —O—, —S— and acombination thereof, provided that both ends are not —O— and —S—, andwhen L¹ is arylene, Z¹ is not arylene. As used herein, alkylene refersto a divalent straight-chain, cyclic or branched chain saturatedhydrocarbon group, and arylene refers to a divalent monocyclic orpolycyclic aromatic hydrocarbon group. Specific examples of alkyleneinclude, for example, methylene, ethylene, propylene, butylene,pentylene, hexylene and octylene and the like. Specific examples ofarylene include, for example, 1,2-phenylene, 1,3-phenylene,1,4-phenylene, biphenyl-4,4′-diyl, diphenylmethane-4,4′-diyl,3,3′-dimethylbiphenyl-4,4′-diyl, 1,2-naphthalene, 1,5-naphthalene,2,6-naphthalene and the like. Moreover, the hydrogen atoms in thesegroups may be replaced by substituents.

In the present invention, Z¹ is preferably methylene, ethylene,propylene, butylene, pentylene, hexylene, cyclohexane-1,4-diyl,1,2-phenylene, 1,3-phenylene, 1,4-phenylene, 1,2-naphthalene,1,5-naphthalene and a linking group composed of two or more of thesedivalent linking groups linked through —O— or —S—, more preferablymethylene, ethylene, propylene, butylene, pentylene, hexylene,1,3-phenylene, 1,4-phenylene, 1,5-naphthalene and a linking groupcomposed of two or more of these divalent linking groups linked through—O—, even more preferably methylene, ethylene, propylene, butylene,pentylene, 1,4-phenylene, —C₂H₄—O—C₂H₄—, —C₂H₄—O—C₂H₄—O—C₂H₄—,—C₂H₄—O-1,4-phenylene-O-1,4-phenylene-O—C₂H₄. Moreover, the hydrogenatoms in these groups may be replaced by substituents.

In formula (a1-0) above, X¹ represents a hydrogen atom or anelectron-releasing group having a Hammett substituent constant op valueof 0.2 or less. The Hammett rule is an experimental rule proposed by L.P. Hammett in 1935 to quantitatively explain the influence ofsubstituents on the reaction or equilibrium of benzene derivatives andcurrently widely recognized as valid. The substituent constantsdetermined by the Hammett rule include up value and am value, which canbe found in many standard books and are described in detail in e.g.,“Lange's Handbook of Chemistry” edited by J. A. Dean, 12th Edition, 1979(Mc Graw-Hill); and “Fields of Chemistry, Extra Issue”, 122, pp. 96-103,1979 (Nankodo Co., Ltd.). It should be understood that varioussubstituents herein are defined or described by the Hammett substituentconstant up, but they are not to be construed as being limited to onlysubstituents having values known from literature found in these books,but also include even substituents having values unknown from literatureso far as they are within the indicated ranges as determined by theHammett rule. The compound of the present invention represented byformula (1) is not a benzene derivative, but the op value is used hereinas a measure indicating the electronic effect of a substituentirrespective of the substituted position. Hereinafter, the op value isused in such meaning. As used herein, the Hammett value is the valuedescribed in “Chemical Seminars 10 Hammett rule—Structure andReactivity—Edited by Naoki Inamoto (1983, published by Maruzen Company,Limited) Specific examples of the electron-releasing group X¹ includealkoxy, aryloxy, anilino, monoalkylamino, hydroxy, trialkylsilyl,trialkylsilyloxy, alkyl, alkenyl, aryl, acylamino, carbamoylamino,alkoxycarbonylamino, 1-aziridinyl, ferrocenyl, and 3-thienyl.

When the X¹ group is an electron-releasing group, the Hammettsubstituent constant op value is preferably in the range of −0.5 to 0.2,more preferably −0.3 to 0.1.

The X¹ group preferably represents a hydrogen atom, alkyl, aryl orheterocyclyl provided that it has a Hammett substituent constant opvalue of 0.2 or less. As used herein, alkyl refers to a straight-chain,branched chain, or cyclic substituted or unsubstituted alkyl, preferablya substituted or unsubstituted C1-30 straight-chain or branched chainalkyl (e.g., methyl, ethyl, isopropyl, n-propyl, n-butyl, t-butyl,2-pentyl, n-hexyl, n-octyl, t-octyl, 2-ethylhexyl, 1,5-dimethylhexyl,n-decyl, n-dodecyl, n-tetradecyl, n-hexadecyl, hydroxyethyl,hydroxypropyl, 2,3-dihydroxypropyl, carboxymethyl, carboxyethyl, sodiumsulfoethyl, diethylaminoethyl, diethylaminopropyl, butoxypropyl,ethoxyethoxyethyl, n-hexyloxypropyl and the like), and a substituted orunsubstituted C3-18 cyclic alkyl (e.g., cyclopropyl, cyclopentyl,cyclohexyl, cyclooctyl, adamantyl, cyclododecyl and the like). Further,a substituted or unsubstituted C5-30 bicycloalkyl (i.e., a monovalentgroup obtained by removing one hydrogen atom from a C5-30 bicycloalkane,e.g., bicyclo[1,2,2]heptane-2-yl, bicyclo[2,2,2]octane-3-yl), andtricyclo structures containing more ring structures and the like arealso included. The aryl preferably refers to a substituted orunsubstituted C6-30 aryl, e.g., phenyl, p-tolyl, nephthyl,m-chlorophenyl, o-hexadecanoylaminophenyl. The heterocyclyl refers to asubstituted or unsubstituted, saturated or unsaturated 5- to 7-memberedheterocyclic ring containing at least one of nitrogen, oxygen and sulfuratoms. These may be a single ring or may form a fused ring system withanother aryl ring or heterocyclic ring. The heterocyclyl is preferably5- to 6-membered, e.g., pyrrolyl, pyrrolidinyl, pyridyl, piperidyl,piperazinyl, imidazolyl, pyrazolyl, pyrazinyl, pyrimidinyl, triazinyl,triazolyl, tetrazolyl, quinolyl, isoquinolyl, indolyl, indazolyl,benzimidazolyl, furyl, pyranyl, chromenyl, thienyl, oxazolyl,oxadiazolyl, thiazolyl, thiadiazolyl, benzoxazolyl, benzothiazolyl,morpholino, morpholinyl and the like.

In the present invention, X¹ is preferably a hydrogen atom, alkyl oraryl, more preferably a hydrogen atom or alkyl, even more preferably ahydrogen atom.

Specific examples of structures represented by formula (a1-0) above inthe present invention are shown below, but the present invention is notlimited to these examples.

The repeating unit (a0) having a structure represented by formula (a1-0)in a side chain includes (meth)acrylic polymers, styryl polymers,polyurethane resins, polyvinyl alcohol resins, polyvinyl formal resins,polyamide resins, polyester resins, epoxy resins and the like.Especially, (meth)acrylic polymers, and styryl polymers are preferred.The repeating unit (a0) having a structure represented by formula (a1-0)in a side chain is preferably a repeating unit represented by formula(A0) below:

In formula (A0), R^(a) to R^(c) each independently represent a hydrogenatom, C1-6 alkyl or halogen atom. The repeating unit (a0) represents astructure represented by formula (a1-0) above, and is attached to acarbon atom of the main chain of formula (A0) at the point indicated bythe asterisk (*) in formula (a1-0) above.

The proportion of (a0) contained in the copolymer (A) is preferably inthe range of 0.01 to 20 mol %, more preferably in the range of 0.01 to10 mol %, even more preferably in the range of 0.01 to 5 mol % based onthe total repeating units to improve staining resistance and printingdurability.

(a1) Repeating unit having a structure represented by formula (a1-1)below in a side chain:

In the lithographic printing plate precursor of the present invention,the copolymer (A) is preferably a copolymer comprising (a1) a repeatingunit having a structure represented by formula (a1-1) below in a sidechain in addition to the repeating unit (a0).

In formula (a1-1), L² represents a divalent covalent linking group,excluding alkylene. Z² represents a covalent linking group selected fromthe group consisting of alkylene, arylene, —O—, —S— and a combinationthereof, provided that —O— and —S— are not terminal, and when L¹ isarylene, Z¹ is not arylene. X² represents a hydrogen atom or anelectron-releasing group having a Hammett substituent constant op valueof 0.2 or less. R represents a substituent. The asterisk (*) indicatesthe point of attachment to the main chain of the polymer compound, i.e.,the copolymer (A)

In formula (a1-1) above, L², Z² and X² have the same meanings as definedfor L¹, Z¹ and X¹ in formula (a1-0) above, and also cover similarpreferred ranges.

In formula (a1-1) above, R represents a substituent. As used herein, thesubstituent refers to include, for example, halogen atoms (fluorineatom, chlorine atom, bromine atom, iodine atom), alkyl, alkenyl,alkynyl, aryl, heterocyclyl, acyl, alkoxycarbonyl, aryloxycarbonyl,heterocyclyloxycarbonyl, carbamoyl, N-hydroxycarbamoyl, N-acylcarbamoyl,N-sulfonylcarbamoyl, N-carbomoylcarbamoyl, thiocarbamoyl,N-sulfamoylcarbamoyl, carbazoyl, carboxy (including salts thereof),oxalyl, oxamoyl, cyano, formyl, hydroxy, alkoxy (including thosecontaining repeated ethyleneoxy or propyleneoxy units), aryloxy,heterocyclyloxy, acyloxy, alkoxycarbonyloxy, aryloxycarbonyloxy,carbamoyloxy, sulfonyloxy, silyloxy, nitro, amino, (alkyl, aryl, orheterocyclyl)amino, acylamino, sulfonamide, ureido, thioureido,N-hydroxyureido, imide, alkoxycarbonylamino, aryloxycarbonylamino,sulfamoylamino, semicarbazide, thiosemicarbazide, hydrazino, ammonio,oxamoylamino, N-(alkyl or aryl)sulfonylureido, N-acylureido,N-acylsulfamoylamino, hydroxyamino, quaternized nitrogen atom-containingheterocyclic group (e.g., pyridinio, imidazolio, quinolinio,isoquinolinio), isocyano, imino, alkylthio, arylthio, heterocyclylthio,(alkyl, aryl, or heterocyclyl)dithio, (alkyl or aryl)sulfonyl, (alkyl oraryl)sulfinyl, sulfo (including salts thereof), sulfamoyl,N-acylsulfamoyl, N-sulfonylsulfamoyl (including salts thereof), silyland the like.

The salts here refer to salts with cations such as alkali metals,alkaline earth metals, heavy metals and the like or salts with organiccations such as ammonium ion, phosphonium ion and the like. Thesesubstituents may be further substituted with these substituents.

In formula (a1-1) above, substituents represented by R preferablyinclude alkyl, alkenyl, alkynyl, aryl, heterocyclyl, acyl,alkoxycarbonyl, aryloxycarbonyl, heterocyclyloxycarbonyl, carbamoyl,thiocarbamoyl, (alkyl or aryl)sulfonyl, (alkyl or aryl)sulfinyl,sulfamoyl and the like, more preferably alkyl, alkenyl, acyl, carbamoyl,(alkyl or aryl)sulfonyl, sulfamoyl and the like, even more preferablyacyl, carbamoyl, (alkyl or aryl)sulfonyl and the like.

In the present invention, the substituent represented by R in formula(a1-1) above is preferably further substituted with a radicallypolymerizable reactive group. Preferred examples of the radicallypolymerizable reactive group here include addition-polymerizableunsaturated bond-containing groups (e.g., (meth)acryloyl,(meth)acrylamide, (meth)acrylonitrile, allyl, vinyl, vinyloxy, alkynyland the like), and chain-transferable functional groups (mercapto andthe like). Among others, addition-polymerizable unsaturatedbond-containing groups are preferred to improve printing durability,more preferably (meth)acryloyl, (meth)acrylamide, and allyl. As usedherein, (meth)acryloyl refers to acryloyl or methacryloyl, and(meth)acrylamide refers to acrylamide or methacrylamide. The use of acopolymer having a radically polymerizable reactive group allowsexcellent developability to be achieved in unexposed areas andpenetration of developers to be prevented by polymerization in exposedareas, thereby further improving adhesion between the substrate and thephotosensitive layer.

Preferably, R represents a group represented by formula (Q) below, or—(C═O)—NR²⁴—CH₂—CH(OH)—R²⁶.

wherein R²¹, R²² and R²³ each independently represent a hydrogen atom,halogen atom or C1-8 alkyl. Preferably, R²¹, R²² and R²³ eachindependently represent a hydrogen atom, C1-6 alkyl or halogen atom (—F,—Br, —Cl, —I). More preferably, at least two of R²¹, R²² and R²³ are ahydrogen atom and the remaining one is a hydrogen atom or C1-6 alkyl.Especially preferably, at least two of R²¹, R²² and R²³ are a hydrogenatom and the remaining one is methyl.R²⁴ represents a hydrogen atom, halogen atom or C1-8 alkyl. Further, R²⁶represents C1-8 alkyl. R²⁴ and R²⁶ may be further substituted, andpreferred substituents include hydroxyl, and the group represented byformula (Q) above.

In the present invention, the structure represented by formula (a1-1)above is preferably a structure generated by the action of a reactivereagent on a structure represented by formula (a1-0) above. Thestructure of formula (a1-1) above can readily be obtained by the actionof a reactive reagent such as, e.g., an acid halide, acid anhydride,mixed acid anhydride, isocyanic acid compound, epoxy compound, sulfonylhalide compound or alkyl halide compound or the like on the structurerepresented by formula (a1-0) above.

Specific examples of structures represented by formula (a1-1) above in(a1) in the present invention are shown below, but the present inventionis not limited to these examples.

The repeating unit (a1) having a struture represented by formula (a1-1)in a side chain preferably has a similar skeleton to that of therepeating unit (a0) having a structure represented by formula (a1-0) ina side chain.

In the present invention, the proportion of the repeating unit (at)having a structure represented by formula (a1-1) above in a side chainbased on the total repeating units constituting the copolymer (A) ispreferably 0 to 70 mol, more preferably 1 to 50 mol %, even morepreferably 5 to 40%. When the repeating unit (a1) having a structurerepresented by formula (a1-1) above in a side chain is a repeating unithaving a radically polymerizable reactive group, it is preferablycontained at 0 to 50 mol %, more preferably 2 to 30 mol %, even morepreferably 5 to 20%. Proportions of 50 mol % or less are preferred forconvenience of preparation because the gelling tendency may decreaseduring synthesis. Further, the repeating unit having a radicallypolymerizable reactive group is preferably not excessive to improvestaining resistance because hydrophilicity is less likely to decrease.On the other hand, printing durability may be more readily improved, ifthe unit is not too little. In view of these points, it is preferablycontained at 5 to 20 mol %.

(a2) Repeating unit having at least one functional group interactingwith the substrate surface:

In addition to the repeating unit (a0) having a structure represented byformula (a1-0) in a side chain, the copolymer (A) preferably comprises(a2) a repeating unit having at least one functional group interactingwith the substrate surface.The functional group interacting with the substrate surface may include,for example, those capable of participating in an interaction such asionic bond formation, hydrogen bond formation or polar interaction witha metal, metal oxide, hydroxyl or the like present on the anodized orhydrophilized substrate.Specific examples of functional groups interacting with the substratesurface are shown below, but the present invention is not limited to thespecific examples below.

In the formulae above, R¹¹ to R¹³ each independently represent ahydrogen atom, C1-10 alkyl, C2-10 alkenyl, C2-10 alkynyl, or C6-15 aryl,and M, M¹ and M² each independently represent a hydrogen atom, a metalatom contained in an alkali metal or an alkaline earth metal orammonium. The functional group interacting with the substrate surface ispreferably the carboxylic acid-containing group, sulfonic acid,phosphoric acid ester or a salt thereof, phosphonic acid or a saltthereof to improve staining resistance and printing durability.

In the lithographic printing plate precursor of the present invention,it is preferably a phosphoric acid ester or a salt thereof or aphosphonic acid or a salt thereof, especially preferably a phosphonicacid or a salt thereof to further improve staining resistance.More preferred examples of the functional group interacting with thesubstrate surface specifically include the structures shown below, butthe present invention is not limited to the specific examples below. Inthe formulae below, the asterisk (*) indicates the point of attachmentto the main chain of the polymer compound.

The repeating unit (a2) having at least one functional group interactingwith the substrate surface is preferably a repeating unit represented byformula (A2) below:

In formula (A2) above, R_(a)′ to R_(c)′ each independently represent ahydrogen atom, C1-6 alkyl or halogen atom. L⁴ represents a single bondor a divalent linking group. Q represents the functional groupinteracting with the substrate surface.

The divalent linking group represented by L⁴ preferably composed of 1 to60 carbon atoms, 0 to 10 nitrogen atoms, 0 to 50 oxygen atoms, 1 to 100hydrogen atoms and 0 to 20 sulfur atoms. More specifically, it is adivalent linking group selected from the group consisting of —O—, —S—,—C(═O)—, —SO₂—, —NH— (wherein the hydrogen atom in —NH— may be replacedby a substituent, and typical examples of substituents include C1-10alkyl and 6-15 aryl), alkylene or arylene, or any combination of thesegroups. The divalent linking group represented by L⁴ is preferably adivalent linking group selected from the group consisting of —O—,—C(═O)—, —NH—, C1-12 alkylene and C6-16 arylene or a combinationthereof, more preferably *—C(═O)—O—, *—C(═O)—NH—, *—C(═O)—O— (CH₂)₂—O—,*—C(═O)—NH—(CH₂)₂—O—, *—C(═O)—O— (CH₂)₂—O— (CH₂)₂—O—, *—C(═O)—NH—(CH₂)₂—O— (CH₂)₂—O—, 1,2-phenylene, 1,3-phenylene, 1,4-phenylene,1,2-naphthalene, 1,5-naphthalene and the like, even more preferably*—C(═O)—O—, *—C(═O)—NH—, *—C(═O)—O— (CH₂)₂—O—, *—C(═O)—NH—(CH₂)₂—O—,1,4-phenylene and the like. The asterisk (*) here indicates the point ofattachment to the main chain of the copolymer (A). Moreover, thehydrogen atoms in these groups may be replaced by substituents. Informula (A2) above, the functional group interacting with the substratesurface represented by Q includes the specific examples mentioned above,and also covers similar preferred examples.

In the copolymer (A), the proportion of the repeating unit (a2) havingat least one functional group interacting with the substrate surface ispreferably in the range of 0 to 99 mol %, more preferably in the rangeof 10 to 95 mol %, even more preferably in the range of 10 to 90 mol %based on the total repeating units to improve staining resistance andprinting durability.

(a3) Repeating unit having a hydrophilic group in a side chain:

In the present invention, the copolymer (A) preferably comprises (a3) arepeating unit having a hydrophilic group in a side chain. Thehydrophilic group is selected from monovalent or divalent or polyvalenthydrophilic groups capable of readily forming a hydrogen bond/van derWaals bond/ionic bond with a water molecule, specifically includinghydroxy, carboxyl, amino, sulfo, positively or negatively chargedgroups, zwitterionic groups and metal salts thereof and the like. Amongthem, hydroxy, sulfonic acid, alkyleneoxy such as ethyleneoxy andpropyleneoxy, quaternary ammonium, amide, ether bond-containing groups,or salts obtained by neutralizing acid groups such as carboxylic acid,sulfonic acid, phosphoric acid and the like, heterocyclic groupscontaining positively charged nitrogen atoms and the like are preferred,for example. These hydrophilic groups may also be used as the repeatingunit (a2) having a structure interacting with the substrate surface in aside chain.

In the present invention, the repeating unit (a3) having a hydrophilicgroup in a side chain is especially preferably a repeating unit having azwitterionic structure in a side chain to confer high hydrophilicity onthe substrate surface of non-image areas.

In the lithographic printing plate precursor of the present invention,the hydrophilic group contained in the copolymer (A) is preferablyselected from zwitterionic structures represented by formula (a3-1) orformula (a3-2) below.

First, the zwitterionic structure represented by formula (a3-1) below isexplained.

In formula (a3-1) above, R³¹ and R³² each independently represent ahydrogen atom, alkyl, alkenyl, alkynyl, aryl or heterocyclyl, or R³¹ andR³² may be joined together to form a ring structure, L³¹ represents adivalent linking group, and A⁻ represents an anion-containing structure.Y³ represents a single bond, or a divalent linking group selected fromthe group consisting of —CO—, —O—, —NH—, a divalent aliphatic group, adivalent aromatic group and a combination thereof. The asterisk (*)indicates the point of attachment to the main chain of the polymercompound.

The ring structure formed by R³¹ and R³² together is preferably a 5- to10-membered ring, more preferably a 5- or 6-membered ring, and maycontain a heteroatom such as oxygen atom and the like.

Preferably, R³¹ and R³² contain 1 to 30 carbon atoms, more preferably 1to 20 carbon atoms, especially preferably 1 to 15 carbon atoms, mostpreferably 1 to 8 carbon atoms including carbon atoms of the optionallypresent substituent described below.

Examples of alkyls represented by R³¹ and R³² include methyl, ethyl,propyl, octyl, isopropyl, t-butyl, isopentyl, 2-ethylhexyl,2-methylhexyl, cyclopentyl and the like. Examples of alkenylsrepresented by R³¹ and R³² include vinyl, allyl, prenyl (e.g.,dimethylallyl, geranyl and the like), oleyl and the like.

Examples of alkynyls represented by R³¹ and R³² include ethynyl,propargyl, trimethylsilylethynyl and the like. Further, examples ofaryls represented by R³¹ and R³² include phenyl, 1-naphthyl, 2-naphthyland the like. Further, examples of heterocyclyls include furanyl,thiophenyl, pyridinyl and the like.

These groups represented by R³¹ and R³² may be further substituted.Examples of substituents include halogen atoms (F, Cl, Br, I), hydroxy,carboxy, amino, cyano, aryl, alkoxy, aryloxy, acyl, alkoxycarbonyl,aryloxycarbonyl, acyloxy, monoalkylamino, dialkylamino, monoarylaminoand diarylamino and the like.

Especially preferred examples of R³¹ and R³² include a hydrogen atom,methyl, or ethyl because of the resulting effect and availability.

The divalent linking group represented by Y³ is a single bond or adivalent linking group selected from the group consisting of —CO—, —C—,—NH—, a divalent aliphatic group, a divalent aromatic group and acombination thereof.

Specific examples L101 to L116 of Y³ consisting of the combinationdescribed above are shown below. In the examples below, each group isattached to the main chain at the left end.

L101: —CO—C— a divalent aliphatic group-L102: —CO—C— a divalent aromatic group-L103: —CO—NH— a divalent aliphatic group-L104: —CO—NH— a divalent aromatic group-L105: —CO— a divalent aliphatic group-L106: —CO— a divalent aromatic group-L107: —CO— a divalent aliphatic group-CO—C— a divalent aliphatic group-L108: —CO— a divalent aliphatic group-C—CO— a divalent aliphatic group-L109: —CO— a divalent aromatic group-CO—C— a divalent aliphatic group-L110: —CO— a divalent aromatic group-C—CO— a divalent aliphatic group-L111: —CO— a divalent aliphatic group-CO—C— a divalent aromatic group-L112: —CO— a divalent aliphatic group-O—CO— a divalent aromatic group-L113: —CO— a divalent aromatic group-CO—C— a divalent aromatic group-L114: —CO— a divalent aromatic group-S—CO— a divalent aromatic group-L115: —CO—O— a divalent aromatic group-O—CO—NH— a divalent aliphaticgroup-L116: —CO—O— a divalent aliphatic group-O—CO—NH— a divalent aliphaticgroup-

The divalent aliphatic group and the divalent aromatic group describedabove refer to include the linking groups mentioned as examples of thedivalent aliphatic group containing 1 to 14 carbon atoms for Z¹, and thelinking groups mentioned as examples of the divalent aromatic groupcontaining 6 to 14 carbon atoms for L¹, respectively. Examples ofsubstituents on the divalent aliphatic group and the divalent aromaticgroup include the substituents with which the groups represented by R³¹and R³² may be further substituted.

Among others, Y³ is preferably a single bond, —CO—, a divalent aliphaticgroup, a divalent aromatic group, or the specific examples L101 to L104shown above. Further, Y³ is preferably L101 or L103 shown above, evenmore preferably L103 to improve staining resistance. Further, thedivalent aliphatic group of L³¹ is preferably a straight-chain alkylenecontaining 2 to 4 carbon atoms, most preferably a straight-chainalkylene containing 3 carbon atoms for convenience of synthesis.

L31 represents a divalent linking group, preferably a linking groupselected from the group consisting of —CO—, —O—, —NH—, a divalentaliphatic group, a divalent aromatic group and a combination thereof,and preferably contains or less carbon atoms including carbon atoms ofthe optionally present substituents described below. Specific examplesthereof include alkylene (preferably containing 1 to 20 carbon atoms,more preferably 1 to 10 carbon atoms), and arylene (preferablycontaining 5 to 15 carbon atoms, more preferably 6 to 10 carbon atoms)such as phenylene, xylylene and the like. Among others, L³¹ ispreferably a straight-chain alkylene containing 3 to 5 carbon atoms,more preferably a straight-chain alkylene containing 4 or 5 carbonatoms, most preferably a straight-chain alkylene containing 4 carbonatoms to improve staining resistance. Specific examples of L³¹ include,for example, the following linking groups:

These linking groups may be further substituted. Examples ofsubstituents include halogen atoms (F, Cl, Br, I), hydroxy, carboxy,amino, cyano, aryl, alkoxy, aryloxy, acyl, alkoxycarbonyl,aryloxycarbonyl, acyloxy, monoalkylamino, dialkylamino, monoarylaminoand diarylamino and the like.

In formula (a3-1) above, A⁻ preferably represents carboxylate,sulfonate, phosphate, phosphonate, or phosphinate.

Specifically, the following anions are included.

To improve staining resistance, A⁻ is most preferably sulfonate.Further, a preferred combination of L³¹ and A⁻ in formula (a1-1) aboveis a combination of a straight-chain alkylene containing 4 or 5 carbonatoms and sulfonate, most preferably a combination of a straight-chainalkylene containing 4 carbon atoms and sulfonate.

In a preferred combination, Y³ is L101 or L103 shown above, R³¹ and R³²are ethyl or methyl, L³¹ is a straight-chain alkylene containing 4 or 5carbon atoms, and A⁻ is sulfonate. In a more preferred combination, Y³is L¹⁰³ shown above, R³¹ and R³² are methyl, L³¹ is a straight-chainalkylene containing 4 carbon atoms, and A⁻ is sulfonate. Thezwitterionic structure represented by formula (a3-1) above specificallyincludes the structures shown below. In the formulae below, the asterisk(*) indicates the point of attachment to the main chain of the copolymer(A).

Next, the zwitterionic structure represented by formula (a3-2) below isexplained.

In formula (a3-2), L³² represents a divalent linking group, and E⁺represents a cation-containing structure. Y⁴ represents a single bond,or a divalent linking group selected from the group consisting of —CO—,—O—, —NH—, a divalent aliphatic group, a divalent aromatic group and acombination thereof. The asterisk (*) indicates the point of attachmentto the main chain of the copolymer.

Also in formula (a3-2) above, L³² represents a divalent linking grouppreferably selected from the group consisting of —CO—, —O—, —NH—, adivalent aliphatic group, a divalent aromatic group and a combinationthereof. Specific examples and preferred examples thereof are the sameas mentioned above for the linking group represented by L³¹

Y⁴ has the same meaning as defined for Y³ in formula (a3-1) above, andalso covers similar preferred examples.E⁺ represents a cation-containing structure, preferably a structurecontaining ammonium or phosphonium, especially preferably a structurecontaining ammonium. Examples of cation-containing structures includetrimethylammonio, triethylammonio, tributylammonio,benzyldimethylammonio, diethylhexylammonio,(2-hydroxyethyl)dimethylammonio, pyridinio, N-methylimidazolio,N-acridinio, trimethylphosphonio, triethylphosphonio,triphenylphosphonio and the like.In a most preferred combination of L³², Y⁴ and E⁺, L³² is an alkylenecontaining 2 to 4 carbon atoms, Y⁴ is L101 or L103 shown above, and E⁺is trimethylammonio or triethylammonio. The zwitterionic structurerepresented by formula (a3-2) specifically includes the structures shownbelow. In the formulae below, the asterisk (*) indicates the point ofattachment to the main chain of the copolymer (A).

In the present invention, the repeating unit having a zwitterionicstructure is preferably a repeating unit represented by (A3) belowspecifically.

wherein R²⁰¹ to R²⁰³ each independently represent a hydrogen atom, C1-6alkyl or halogen atom. G represents a side chain having a zwitterionicstructure, preferably a structure represented by formula (a3-1) or(a3-2) above. Preferred examples and combinations of formulae (a3-1) and(a3-2) are as described above.

In formula (A3) above, the side chain G especially preferably has astructure represented by formula (a3-1)

In the present invention, the proportion of the repeating unit (a3)having a hydrophilic group in a side chain based on the total repeatingunits constituting the copolymer (A) is preferably in the range of 5 to95 mol %, more preferably in the range of 5 to 80 mol %, even morepreferably in the range of 10 to 70 mol % to improve hydrophilicity.

Extra repeating unit:

Further, the copolymer (A) may comprise an extra repeating unit otherthan the repeating units described above (hereinafter also referred toas an “extra repeating unit”) as a component of a copolymer. Extrarepeating units that may be contained as such repeating units includerepeating units derived from various known monomers.Preferred examples include repeating units derived from known monomerssuch as acrylic acid esters, methacrylic acid esters, acrylamides,methacrylamides, vinyl esters, styrenes, acrylic acid, methacrylic acid,acrylonitrile, maleic anhydride, maleimide and the like. Variousproperties of the layers such as film-forming properties, film strength,hydrophilicity, hydrophobicity, solubility, reactivity, stability andthe like can be improved or controlled as appropriate by introducing theextra repeating unit into the copolymer (A).

Specific examples of the acrylic acid esters include methyl acrylate,ethyl acrylate, (n- or i-)propyl acrylate, (n-, i-, sec- or t-)butylacrylate, amyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate,chloroethyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate,2-hydroxypentyl acrylate, cyclohexyl acrylate, allyl acrylate,trimethylolpropane monoacrylate, pentaerythritol monoacrylate, benzylacrylate, methoxybenzyl acrylate, chlorobenzyl acrylate, hydroxybenzylacrylate, hydroxyphenethyl acrylate, dihydroxyphenethyl acrylate,furfuryl acrylate, tetrahydrofurfuryl acrylate, phenyl acrylate,hydroxyphenyl acrylate, chlorophenyl acrylate, sulfamoylphenyl acrylate,2-(hydroxyphenylcarbonyloxy)ethyl acrylate, polyalkylene glycol acrylateand the like.

Specific examples of the methacrylic acid esters include methylmethacrylate, ethyl methacrylate, (n- or i-)propyl methacrylate, (n-,i-, sec- or t-)butyl methacrylate, amyl methacrylate, 2-ethylhexylmethacrylate, dodecyl methacrylate, chloroethyl methacrylate,2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate,2-hydroxypentyl methacrylate, cyclohexyl methacrylate, allylmethacrylate, trimethylolpropane monomethacrylate, pentaerythritolmonomethacrylate, benzyl methacrylate, methoxybenzyl methacrylate,chlorobenzyl methacrylate, hydroxybenzyl methacrylate, hydroxyphenethylmethacrylate, dihydroxyphenethyl methacrylate, furfuryl methacrylate,tetrahydrofurfuryl methacrylate, phenyl methacrylate, hydroxyphenylmethacrylate, chlorophenyl methacrylate, sulfamoylphenyl methacrylate,2-(hydroxyphenylcarbonyloxy)ethyl methacrylate, polyalkylene glycolmethacrylate and the like.

Specific examples of the acrylamides include acrylamide, N-methylacrylamide, N-ethyl acrylamide, N-propyl acrylamide, N-butyl acrylamide,N-benzyl acrylamide, N-hydroxyethyl acrylamide, N-phenyl acrylamide,N-tolyl acrylamide, N-(hydroxyphenyl)acrylamide,N-(sulfamoylphenyl)acrylamide, N-(phenylsulfonyl)acrylamide,N-(tolylsulfonyl)acrylamide, N,N-dimethyl acrylamide, N-methyl-N-phenylacrylamide, N-hydroxyethyl-N-methyl acrylamide, polyalkylene glycolacrylamide and the like.

Specific examples of the methacrylamides include methacrylamide,N-methyl methacrylamide, N-ethyl methacrylamide, N-propylmethacrylamide, N-butyl methacrylamide, N-benzyl methacrylamide,N-hydroxyethyl methacrylamide, N-phenyl methacrylamide, N-tolylmethacrylamide, N-(hydroxyphenyl)methacrylamide,N-(sulfamoylphenyl)methacrylamide, N-(phenylsulfonyl)methacrylamide,N-(tolylsulfonyl)methacrylamide, N,N-dimethyl methacrylamide,N-methyl-N-phenyl methacrylamide, N-hydroxyethyl-N-methylmethacrylamide, polyalkylene glycol methacrylamide and the like.

Specific examples of the vinyl esters include vinyl acetate, vinylbutyrate, vinyl benzoate and the like. Specific examples of styrenesinclude styrene, methylstyrene, dimethylstyrene, trimethylstyrene,ethylstyrene, propylstyrene, cyclohexylstyrene, chloromethylstyrene,trifluoromethylstyrene, etoxymethylstyrene, acetoxymethylstyrene,methoxystyrene, dimethoxystyrene, chlorostyrene, dichlorostyrene,bromostyrene, iodostyrene, fluorostyrene, carboxystyrene and the like.

In the copolymer (A), the proportion of the extra repeating unit ispreferably 0 to 60 mol %, more preferably to 40 mol %, even morepreferably 0 to 30%.

(Weight Average Molecular Weight)

The weight average molecular weight (Mw) of the copolymer (A) can beappropriately selected depending on the performance design of thelithographic printing plate precursor. To improve printing durabilityand staining resistance, the weight average molecular weight ispreferably 2,000 to 1,000,000, more preferably 2,000 to 500,000, mostpreferably 8,000 to 300,000.

Specific examples of the copolymer (A) are shown below along with theirweight average molecular weights, but the present invention is notlimited to these examples. It should be noted that the composition ratioof the polymer structures are expressed in molar percentage.

(Processes for Preparing the Copolymer (A))

The copolymer (A) can be synthesized by known methods, but preferably byusing radical polymerization followed by ureation reaction using theamino group in a polymer side chain and an isocyanate having a radicallypolymerizable reactive group.

Typical techniques for radical polymerization are described in, forexample, “New Polymer Experimental Chemistry, vol. 3” (Edited by theSociety of Polymer Science, Japan, published by KYORITSU SHUPPAN CO.,LTD., Mar. 28, 1996); “Synthesis and Reaction of Polymers, vol. 1”(Edited by the Society of Polymer Science, Japan, published by KYORITSUSHUPPAN CO., LTD., May 1992); “New Textbook of Experimental Chemistry,vol. 19, Polymer Chemistry (I) (Edited by the Chemical Society of Japan,published by Maruzen Company, Limited, Nov. 20, 1980); “Textbook ofMaterial Engineering, Polymer Synthetic Chemistry” (published by TokyoDenki University Press, September 1995) and the like, and thesetechniques can be applied.

(B) Polymerization Initiator

The polymerization initiator (hereinafter also referred to as an“initiator compound”) used in the present invention is contained in thephotosensitive layer. In the present invention, a radical polymerizationinitiator is preferably used. The preferred range and amount to be addedand the like of the polymerization initiator can be determined byreference to the description of the first embodiment hereinabove.

(C) Polymerizable Compound

The preferred range and amount to be added and the like of the (C)polymerizable compound used in the photosensitive layer can bedetermined by reference to the description of the first embodimenthereinabove.

(D) Binder

The preferred range and amount to be added and the like of the (D)binder contained in the photosensitive layer of the lithographicprinting plate precursor of the present invention can be determined byreference to the description of the first embodiment hereinabove.

(E) Sensitizing Dye

The photosensitive layer preferably contains a sensitizing dye.The preferred range and amount to be added and the like of the (E)sensitizing dye used in the photosensitive layer of the lithographicprinting plate precursor of the present invention can be determined byreference to the description of the first embodiment hereinabove.

(F) Other Components in the Photosensitive Layer

The photosensitive layer can further contain various additives, asappropriate. The additives that can be added include surfactants forpromoting developability and improving the profile of coating surfaces,microcapsules for improving both developability and printing durability,hydrophilic polymers for improving developability or improvingdispersion stability of microcapsules or the like, colorants orprinting-out agents for visually identifying image areas and non-imageareas, polymerization inhibitors for inhibiting undesired thermalpolymerization of radically polymerizable compounds during preparationor storage of the photosensitive layer, higher fatty acid derivativesfor preventing polymerization inhibition by oxygen, inorganicmicroparticles for improving the strength of cured films of image areas,hydrophilic low-molecular weight compounds for improving developability,co-sensitizers or chain transfer agents for improving sensitivity,plasticizers for improving plasticity and the like. All these compoundsare known and available, including e.g., the compounds described inparagraphs [0161] to [0215] of JP-A2007-206217.

(Formation of the Photosensitive Layer)

The photosensitive layer in the lithographic printing plate precursor ofthe present invention can be formed by any known method without specificlimitation. Specifically, further information can be found in thedescription of the first embodiment hereinabove.

Substrate

The substrate used in the lithographic printing plate precursor of thepresent invention is not specifically limited, and any hydrophilicplate-like substrates having a stable size may be used. Specifically,further information can be found in the description of the firstembodiment hereinabove.

<Hydrophilization>

In the lithographic printing plate precursor of the present invention,the surface of the substrate may preferably be hydrophilized to improvehydrophilicity and prevent print staining in non-image areas.Specifically, further information can be found in the description of thefirst embodiment hereinabove.

[Extra Layer Optionally Provided Between the Substrate and thePhotosensitive Layer]

In the lithographic printing plate precursor of the present invention, aprimer layer may preferably be provided between the substrate and thephotosensitive layer to improve hydrophilicity and prevent printstaining in non-image areas.

<Primer Layer>

When the lithographic printing plate precursor of the present inventioncomprises a primer layer, the primer layer preferably contains thecopolymer (A). Details of the primer layer can be found in thedescription of the first embodiment hereinabove.

[Protective Layer]

In the lithographic printing plate precursor of the present invention, aprotective layer (oxygen barrier layer) is preferably provided on thephotosensitive layer to block diffusion and penetration of oxygendetrimental to polymerization reaction during exposure. Details of theprotective layer can be found in the description of the first embodimenthereinabove.

[Back Coating Layer]

The lithographic printing plate precursor of the present invention maycomprise a back coating layer on the bottom of the substrate asappropriate. The back coating layer preferably includes, for example,the coating layers made of an organic polymer compound described inJP-A-H5-45885 or a metal oxide obtained by hydrolyzing andpolycondensing an organic metal compound or an inorganic metal compounddescribed in JP-A-H6-35174. Among them, silicon alkoxide compounds suchas Si(OCH₃)₄, Si(OC2H₅)₄, Si(OC₃H₇)₄, and Si(OC₄H₉)₄ are preferably usedbecause the source materials are inexpensive and readily available.

[Processes for Preparing Lithographic Printing Plates]

First Embodiment

Lithographic printing plates can be prepared by image-exposing alithographic printing plate precursor according to the first embodimentof the present invention and developing it.An example of a process for preparing a lithographic printing plateaccording to a first embodiment of the present invention comprises:image-exposing a lithographic printing plate precursor of the presentinvention; and developing the exposed lithographic printing plateprecursor in a developer having a pH of 2 to 14; wherein the developingcomprises removing unexposed areas of the photosensitive layer and theprotective layer simultaneously in the presence of the developer.

Preferably, the process for preparing a lithographic printing plate ofthe present invention comprises forming a protective layer on thesurface of the photosensitive layer opposite to the substrate; whereinthe developing comprises removing the photosensitive layer in unexposedareas and the protective layer simultaneously in the presence of thedeveloper further containing a surfactant without includingwater-washing.

Another example of the process for preparing a lithographic printingplate according to the first embodiment of the present inventioncomprises: image-exposing a lithographic printing plate precursor of thepresent invention; and supplying a printing ink and a dampening water toremove the photosensitive layer in unexposed areas on a printing press.Preferred aspects of each of the process for preparing a lithographicprinting plate according to the first embodiment of the presentinvention are explained in order below. Additionally, lithographicprinting plates can also be prepared from the lithographic printingplate precursor of the present invention by the process for preparing alithographic printing plate of the present invention when the developingincludes water-washing.

<Exposure>

The method of manufacturing the lithographic printing plate of thepresent invention includes exposing the lithographic printing plateprecursor according to the present invention in a pattern-wise manner.The lithographic printing plate precursor according to the presentinvention is exposed by laser shot through a transparent original havinga line image or halftone image or the like, or laser scanning modulatedby digital data.

Wavelength of light source is preferably 300 to 450 nm or 750 to 1400nm. When the light source of 300 to 450 nm is used, the lithographicprinting plate precursor preferably contains, in the photosensitivelayer thereof, a sensitizing dye showing an absorption maximum in thiswavelength. On the other hand, for the case where the light source of750 to 1400 nm is used, the lithographic printing plate precursorpreferably contains, in the photosensitive layer thereof, an infraredabsorber, which is a sensitizing dye showing an absorption maximum inthis wavelength range. The light source of 300 to 450 nm is preferably asemiconductor laser. The light source of 750 to 1400 nm is preferably asolid-state laser or semiconductor laser capable of emitting infraredradiation. The infrared laser preferably has an output of 100 mW orlarger, exposure time per pixel is preferably 20 microseconds orshorter, and exposure energy is preferably 10 to 300 mJ/cm². Amulti-beam laser device is preferably used in order to shorten theexposure time. An exposure mechanism may be based on Any of internaldrum system, external drum system, and flat bed system.

The pattern-wise exposure may be proceeded by a general method using aplate setter, for example. When the on-machine development is adopted,the lithographic printing plate precursor may be set on a printingmachine and may be exposed pattern-wise on the printing machine.

<Development>

The development may be implemented by (1) a method of development usinga developer of pH2 to 14 (developer process), or (2) a method ofdevelopment on a printing machine, while feeding fountain solutionand/or ink (on-machine development).

(Developer Process)

In the developer process, the lithographic printing plate precursor istreated using the developer of pH2 to 14, so as to remove the unexposedarea of the photosensitive layer, and thereby lithographic printingplate is manufactured.

In a general process of development using a strong alkaline developer(pH12 or above), the protective layer is removed by pre-water washing,subjected to alkaline development, post-water washing for removingalkali by water washing, gum solution treatment, and drying process, tothereby obtain the lithographic printing plate. According to a firstpreferable embodiment of the present invention, the developer usedherein has pH value of 2 to 14. In this embodiment, the developerpreferably contains a surfactant or water-soluble polymer compound, soas to concomitantly allow the development and gum solution treatment toproceed. Accordingly, the post-water washing is not indispensable, andthe development and the gum solution treatment may be proceeded in asingle solution.

Also the pre-water washing is not indispensable, so that also theremoval of the protective layer may be proceeded concomitantly with thegum solution treatment. In the method of manufacturing the lithographicprinting plate of the present invention, the development and gumsolution treatment is preferably followed by removal of excessivedeveloper using a squeeze roller for example, and drying.

The development by developer in the lithographic printing plateprecursor of the present invention may be proceeded as usual at 0 to 60°C., preferably 15 to 40° C. or around, typically by a method of dippingthe exposed lithographic printing plate precursor into a developerfollowed by rubbing with a brush, or a method of spraying a developerfollowed by rubbing with a brush.

The development using the developer is successfully implemented on anautomatic processor, equipped with a developer feeder and a rubbingmember. The automatic processor having rotating brush rollers as therubbing member is particularly preferable. The automatic processorpreferably has a unit for removing excessive developer, such as squeezerollers, and a drying unit such as a hot air blower, on the downstreamside of the developing unit. Moreover, the automatic processor may havea pre-heating unit for heating the exposed lithographic printing plateprecursor, on the upstream side of the developing unit.

An example of automatic processor used for the method of manufacturing alithographic printing plate of the present invention will be briefedbelow, referring to FIG. 1.

The example of the automatic processor used for the method ofmanufacturing a lithographic printing plate of the present invention isillustrated in FIG. 1. The automatic processor illustrated in FIG. 1 isbasically composed of a developing unit 6 and a drying unit 10, whereinthe lithographic printing plate precursor 4 is developed in thedeveloping tank 20, and dried in the drying unit 10.

The automatic processor 100 illustrated in FIG. 2 is composed of achamber shaped by an equipment frame 202, and has a pre-heating section200, a developing section 300 and a drying section 400 aligned in linein the direction of a feed path 11 along which the lithographic printingplate precursor is fed (indicated by arrow A).

The pre-heating section 200 has a heating chamber 208 with a feedingport 212 and an output port 218, and has tandem rollers 210, heaters 214and a circulating fan 216 arranged therein.

The developing section 300 is partitioned by an outer panel 310 from thepre-heating section 200, and the outer panel 310 has an insertion slit312.

Inside the developing section 300, there is provided a process tank 306having therein a developing tank 308 filled with a developer, and aninsertion roller pair 304 for guiding the lithographic printing plateprecursor into the process tank 306. The upper portion of the developingtank 308 is covered with a shielding lid 324.

Inside the developing tank 308, there is provided a guide roller 344 anda guiding member 342, an immersed roller pair 316, a brush roller pair322, a brush roller pair 326, and an output roller pair 318 which arealigned in sequence from the upstream side of the feeding direction. Thelithographic printing plate precursor brought into the developing tank308 is dipped in the developer, and allowed to pass through the rotatingbrush roller pairs 322, 326, to be removed with the non-image-formingarea.

Below the brush roller pairs 322, 326, there is provided a spray pipe330. The spray pipe 330 is connected to a pump (not illustrated), andthe developer in the developing tank 308 sucked up by the pump isejected through the spray pipe 330 into the developing tank 308.

On the sidewall of the developing tank 308, there is provided anoverflow port 51 opened at the top end portion of a first circulatingpipe C1, so as to allow an excessive portion of the developer to flowinto the overflow port 51, run down through the first circulating pipeCl, to be discharged into an external tank 50 provided outside thedeveloping section 300.

The external tank 50 is connected to a second circulating pipe C2. Thesecond circulating pipe C2 is provided with a filter unit 54 and adeveloper feed pump 55. By the developer feed pump 55, the developer isfed from the external tank 50 to the developing tank 308. The externaltank 50 is provided with a upper level gauge 52 and a lower level gauge53.

The developing tank 308 is connected through a third circulating pipe C3to a supplementary water tank 71. The third circulating pipe C3 isprovided with a water supplement pump 72 by which water reserved in thesupplementary water tank 71 is fed to the developing tank 308.

A liquid temperature sensor 336 is provided on the upstream side of theimmersed roller pair 316, and a level gauge 338 is provided on theupstream side of the output roller pair 318.

A partition board 332 placed between the developing section 300 and thedrying section 400 has an insertion slit provided thereto. On a pathbetween the developing section 300 and the drying section 400, there isprovided a shutter (not illustrated) which closes the path when thelithographic printing plate precursor 11 does not travel on the path.

The drying section 400 has a support roller 402, ducts 410, 412, a feedroller pair 406, ducts 410, 412, and a feed roller pair 408 alignedtherein in sequence. Each of the ducts 410, 412 has a slit hole 414provided to the tip thereof. The drying section 400 has provided theretoan unillustrated drying unit such as a hot air blower, heat generator orthe like. The drying section 400 has a discharge port 404, through whichthe lithographic printing plate dried by the drying unit is ejected.

In the present invention, the developer used for the development bydeveloper is preferably an aqueous solution of pH2 to 14, or contains asurfactant. The developer is preferably an aqueous solution mainlycomposed of water (with a water content of 60% by mass or more), whereinan aqueous solution containing a surfactant (anionic, nonioic, cationic,ampholytic ion-based, etc.), or an aqueous solution containing awater-soluble polymer compound is particularly preferable. Also anaqueous solution containing both of surfactant and water-soluble polymercompound is preferable. The developer is preferably pH3.5 to 13, morepreferably pH6 to 13, and particularly pH6.5 to 10.5. In particular, forthe case where the developer of pH2.0 to 10.0 is used, it is difficultto concomitantly preventing all of staining resistance, printingdurability, and long-term staining resistance from degrading. The reasonwhy may be explained as below. When species of the developer is tried tochange, while leaving the material for composing the lithographicprinting plate precursor unchanged, the developer of pH2.0 to 10.0 willdegrade the staining resistance of the unexposed area, as compared withthe case where the conventional alkali developer of pH12 to 13 was used.

The anionic surfactant used for the developer in the present inventionis not specifically limited and is preferably selectable from fatty acidsalts, abietate salts, hydroxyalkanesulfonate salts, alkanesulfonatesalts, dialkylsulfosuccinate salts, straight-chain alkylbenzenesulfonatesalts, branched alkylbenzenesulfonate salts, alkylnaphthalenesulfonatesalts, alkyl diphenyl ether (di)sulfonate salts,alkylphenoxypolyoxyethylenealkylsulfonate salts,polyoxyethylenealkylsulfophenyl ether salts, sodium salts ofN-alkyl-N-oleyltaurin, disodium salts of N-alkyl sulfolsuccinatemonoamide, petroleum sulfonate salts, sulfated castor oil, sulfated beeftallow, sulfate ester salts of fatty acid alkyl ester, alkyl sulfateester salts, polyoxyethylenealkyl ether sulfate ester salts, fatty acidmonoglyceride sulfate ester salts, polyoxyethylenealkylphenyl ethersulfate ester salts, polyoxyethylenestyrylphenyl ether sulfate estersalts, alkylphosphoester salts, polyoxyethylenealkyl ether phosphoestersalts, polyoxyethylenealkylphenyl ether phosphoester salts, partiallysaponified styrene-maleic anhydride copolymer, partially saponifiedolefin-maleic anhydride copolymer, and naphthalene sulfonatesalt-formalin condensates. Among them, alkylbenzenesulfonate salts,alkylnaphthalenesulfonate salts, and alkyldiphenyl ether (di)sulfonatesalts are particularly preferable.

The cationic surfactant used for the developer in the present inventionis arbitrarily selectable from those known in the art, without speciallimitation. The examples include alkylamine salts, quaternary ammoniumsalts, alkylimidazolinium salt, polyoxyethylene alkylamine salts, andpolyethylene polyamine derivative.

The nonionic surfactant used for the developer in the present inventionis not specifically limited, and is selectable from ethylene oxideadduct of polyethylene glycol-type higher alcohol, ethylene oxide adductof alkylphenol, ethylene oxide adduct of alkylnaphthol, ethylene oxideadduct of phenol, ethylene oxide adduct of naphthol, ethylene oxideadduct of fatty acid, ethylene oxide adduct of polyhydric alcohol fattyacid ester, ethylene oxide adduct of higher alkylamine, ethylene oxideadduct of fatty acid amide, ethylene oxide adduct of fat, ethylene oxideadduct of polypropylene glycol, dimethylsiloxane-ethylene oxide blockcopolymer, dimethylsiloxane-(propylene oxide-ethylene oxide) blockcopolymer, fatty acid ester of polyhydric alcohol-type glycerol, fattyacid ester of pentaerythritol, fatty acid ester of sorbitol andsorbitan, fatty acid ester of sucrose, polyhydric alcohol alkyl ether,and fatty acid amide of alkanolamines. Among them, those having anaromatic ring and an ethylene oxide chain are preferable, and morepreferable examples include ethylene oxide adduct of alkyl substitutedor unsubstituted phenol, or ethylene oxide adduct of alkyl substitutedor unsubstituted naphthol.

The ampholytic-ion-based surfactant used for the developer in thepresent invention is not specifically limited, and is selectable fromamine oxide-based surfactant such as alkyldimethylamine oxide;betaine-based surfactant such as alkyl betaine; and amino acid-basedsurfactant such as sodium salt of alkylaminofatty acid. In particular,alkyl dimethylamine oxide which may have a substituent group, alkylcarboxybetaine which may have a substituent group, and alkylsulfobetaine which may have a substituent group are preferably used.More specifically, the compounds represented by the formula (2) inparagraph [0256] of Japanese Laid-Open Patent Publication No.2008-203359; the compounds represented by the formula (I), formula (II)and formula (VI) in paragraph [0028] of Japanese Laid-Open PatentPublication No. 2008-276166; and the compounds described in paragraphs[0022] to [0029] of Japanese Laid-Open Patent Publication No. 2009-47927may be used.

Two or more species of the surfactant may be used in the developer. Thecontent of the surfactant contained in the developer is preferably 0.01to 20% by mass, and more preferably 0.1 to 10% by mass.

Examples of the water-soluble polymer compound used for the developer inthe present invention include soybean polysaccharides, modified starch,gum arabic, dextrin, cellulose derivative (carboxymethyl cellulose,carboxyethyl cellulose, methyl cellulose, etc.) and modified productthereof, pullulan, polyvinyl alcohol and derivative thereof,polyvinylpyrrolidone, polyacrylamide and acrylamide copolymer, vinylmethyl ether/maleic anhydride copolymer, vinyl acetate/maleic anhydridecopolymer, styrene/maleic anhydride copolymer, polyvinylsulfonic acidand salt thereof, and polystyrenesulfonic acid and salt thereof.

The soybean polysaccharides are selectable from those known in the art,such as those commercially available under the trade name of Soyafive(from Fuji Oil Co. Ltd.) with a variety of grades. Among them, thoseshowing a viscosity of a 10% by mass aqueous solution of 10 to 100mPa/sec are preferably used.

Also the modified starch is selectable from those known in the art,which may be prepared for example by decomposing starch derived fromcorn, potato, tapioca, rice, wheat or the like by acid or enzyme, so asto give molecules having 5 to 30 glucose residues, and by adding theretooxypropylene in an alkaline solution.

Two or more species of the water-soluble polymer compounds may be usedin the developer. The content of the water-soluble polymer compound inthe developer is preferably 0.1 to 20% by mass, and more preferably 0.5to 10% by mass.

The developer used in the present invention may contain a pH bufferingagent. For the developer of the present invention, the pH bufferingagent is arbitrarily selectable without special limitation, so long asit exhibits a buffering action in the range from pH2 to 14. In thepresent invention, a weak alkaline buffering agent is preferably used,wherein the examples include (a) carbonate ion and hydrogen carbonateion, (b) borate ion, (c) water-soluble amine compound and ion thereof,and combination of these ions. More specifically, (a) combination ofcarbonate ion and hydrogen carbonate ion, (b) borate ion, or (c)combination of water-soluble amine compound and ion thereof, forexample, exhibits a pH buffering action in the developer, capable ofsuppressing pH from fluctuating even if the developer is used over along period, and is therefore capable of suppressing degradation in thedevelopability and generation of development scum due to fluctuation inpH. In the method of manufacturing the lithographic printing plate ofthe present invention, the combination of carbonate ion and hydrogencarbonate ion is particularly preferable.

In order to allow carbonate ion and hydrogen carbonate ion to reside inthe developer, one possible method is to add a carbonate salt and ahydrogen carbonate salt into the developer, and another method is toadjust pH after the carbonate salt or hydrogen carbonate salt are added,so as to generate carbonate ion or hydrogen ion. While the carbonatesalt and the hydrogen carbonate salt are not specifically limited,alkali metal salt is preferable. The alkali metal is exemplified bylithium, sodium, and potassium, wherein sodium is particularlypreferable. The alkali metal may be used alone, or in combination of twoor more species.

Total content of carbonate ion and hydrogen carbonate ion is preferably0.05 to 5 mol/L in the developer, more preferably 0.07 to 2 mol/L, andparticularly 0.1 to mol/L.

The developer used in the present invention may contain an organicsolvent. Examples of the organic solvent adoptable herein includealiphatic hydrocarbons (hexane, heptane, Isopar E, Isopar H, Isopar G(from Esso), etc.), aromatic hydrocarbon (toluene, xylene, etc.),halogenated hydrocarbon (methylene dichloride, ethylene dichloride,trichloroethylene, monochlorobenzene, etc.), and polar solvent. Examplesof the polar solvent include alcohols (methanol, ethanol, propanol,isopropanol, 1-butanol, 1-pentanol, 1-hexanol, 1-heptanol, 1-octanol,2-octanol, 2-ethyl-1-hexanol, 1-nonanol, 1-decanol, benzyl alcohol,ethylene glycol monomethyl ether, 2-ethoxyethanol, diethylene glycolmonoethyl ether, diethylene glycol monohexyl ether, triethylene glycolmonomethyl ether, propylene glycol monoethyl ether, propylene glycolmonomethyl ether, polyethylene glycol monomethyl ether, polypropyleneglycol, tetraethylene glycol, ethylene glycol monobutyl ether, ethyleneglycol monobenzyl ether, ethylene glycol monophenyl ether, propyleneglycol monophenyl ether, methylphenyl carbinol, n-amyl alcohol,methylamyl alcohol, etc.); ketones (acetone, methyl ethyl ketone, ethylbutyl ketone, methyl isobutyl ketone, cyclohexanone, etc.); esters(ethyl acetate, propyl acetate, butyl acetate, amyl acetate, benzylacetate, methyl lactate, butyl lactate, ethylene glycol monobutylacetate, propylene glycol monomethyl ether acetate, diethylene glycolacetate, diethyl phthalate, butyl levulinate, etc.); and others(triethyl phosphate, tricresyl phosphate, N-phenylethanolamine,N-phenyldiethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine,4-(2-hydroxyethyl)morpholine, N,N-dimethylacetamide,N-methylpyrrolidone, etc.).

Two or more species of the organic solvent may be contained in thedeveloper. If the organic solvent is not water-soluble, it may be usedafter solubilizing it into water with the aid of the surfactant or thelike. When the developer contains the organic solvent, the content ofthe organic solvent is preferably less than 40% by mass, from theviewpoint of safety and inflammability.

Besides the above-described components, the developer of the in thepresent invention may also contain antiseptic, chelating compound,defoamer, organic acid, inorganic acid, inorganic salt and so forth.More specifically, the compounds described in paragraphs [0266] to[0270] of Japanese Laid-Open Patent Publication No. 2007-206217 arepreferably used.

In the present invention, the developer may be used both as a developerand a supplementary developer for the lithographic printing plateprecursor. It is also preferably adoptable to the automatic processordescribed in the above. In the process of development on the automaticprocessor, since the developer is exhausted with the progress ofdevelopment, so that the supplementary solution or fresh developer maybe used to restore the process capacity.

<On-Machine Development System>

In the on-machine development system, the lithographic printing plateprecursor after pattern-wise exposure is fed, on a printing machine,with an oil-based ink and water-based component, so as to remove thephotosensitive layer selectively in the non-image-forming area, tothereby give a lithographic printing plate.

More specifically, the lithographic printing plate precursor is exposedpattern-wise and then set on the printing machine without development,or, the lithographic printing plate precursor is set on the printingmachine and then exposed pattern-wise on the printing machine. Next,printing is started by feeding the oil-based ink and the water-basedcomponent. In the non-image-forming area, the uncured photosensitivelayer is removed in the early stage of printing, by dissolution ordispersion with the aid of the oil-based ink and/or water-basedcomponent fed thereto, and thereby the hydrophilic surface exposes inthe area. On the other hand, in the light-exposed area, thephotosensitive layer cured by exposure forms an acceptance sites foroil-based ink where a lipophilic surface exposes. While it is arbitrarywhich of the oil-based ink and the water-based component is the first tobe fed onto the surface of plate, it is more preferable to feed theoil-based ink first, in view of preventing the water-based componentfrom being contaminated by components of the removed photosensitivelayer. In this way, the lithographic printing plate precursor isdeveloped on the printing machine, and is directly used in a largenumber of impressions. The oil-based ink and the water-based componentare preferably a printing ink and fountain solution, respectively, whichare used for general planographic printing.

In the method of manufacturing a lithographic printing plate from alithographic printing plate precursor according to the presentinvention, the entire surface of the lithographic printing plateprecursor may be heated before exposure, or during exposure, or betweenexposure and development, irrespective of the development style. By theheating, the image forming reaction in the recording layer may beaccelerated, to thereby advantageously improve the sensitivity andprinting durability, and stabilize the sensitivity. For the developmentby developer, it is also effective to subject the developed plate topost-heating or exposure over the entire surface, aiming at improvingthe strength of the image-forming area and printing durability. Ingeneral, the pre-heating is preferably proceeded under a mild conditiontypically at 150° C. or lower. Too high temperature may result in curingof the non-image-forming area. On the other hand, the post-heating afterdevelopment needs a very strong condition, typically at 100 to 500° C.Too low temperature may result in insufficient strength of theimage-forming area, whereas too high temperature may degrade thesupport, or decompose the image-forming area.

Second Embodiment

Alternatively, lithographic printing plates can be prepared byimage-exposing a lithographic printing plate precursor according to thesecond embodiment of the present invention and developing it.Preferred aspects of each of the process for preparing a lithographicprinting plate according to the second embodiment of the presentinvention are explained in order below. Additionally, lithographicprinting plates can also be prepared from the lithographic printingplate precursor of the present invention when the developing includes awater-washing though such a variation departs from the original purposeof the process for preparing a lithographic printing plate of thepresent invention.

<Exposure>

The process for preparing a lithographic printing plate of the presentinvention comprises image-exposing a lithographic printing plateprecursor of the present invention. Details of the exposure can be foundin the description of the first embodiment hereinabove.

<Developing>

The process for preparing a lithographic printing plate of the presentinvention comprises developing the exposed lithographic printing plateprecursor in a developer containing a surfactant, wherein the developingcomprises removing unexposed areas of the photosensitive layer and theprotective layer simultaneously in the presence of the developer. Such adevelopment process using a developer is referred to as developerprocess. In the developer process, the image-exposed lithographicprinting plate precursor is treated with a developer containing asurfactant, whereby the photosensitive layer in unexposed areas isremoved to prepare a lithographic printing plate.The process for preparing a lithographic printing plate of the presentinvention may or may not comprise water-washing, but preferably does notcomprise water-washing.Conventional development processes using highly alkaline developers (pH12 or more) typically comprise removing the protective layer bypre-washing with water, then alkaline development, washing away thealkali by post-washing with water, treatment with a gum solution, anddrying to prepare a lithographic printing plate. In contrast, apreferred aspect of the process for preparing a lithographic printingplate of the present invention does not comprise these water-washing.The developer containing a surfactant allows development and gumsolution treatment to be performed simultaneously, and eliminates thenecessity of post-washing with water, whereby development and gumsolution treatment can be performed with only one chemical solution.Further, it also eliminates the necessity of pre-washing with water,whereby removal of the protective layer can also be performedsimultaneously with development and gum solution treatment.According to a preferred aspect of the present invention, a developerhaving a pH of 2.0 to 10.0 is used. In this aspect, the developerpreferably contains a surfactant, or a surfactant and a water-solublepolymer compound, whereby development and gum solution treatment takeplace simultaneously using only one chemical solution. Further, evenwhen a developer having a pH of 2.0 to 10.0 is used, pre-washing withwater may not be required so that removal of the protective layer canalso take place simultaneously with development and gum solutiontreatment. In the process for preparing a lithographic printing plate ofthe present invention, the development and gum solution treatment arepreferably followed by removal of an excess of the developer by using,for example, a squeeze roller, and then drying.

The developer process of the lithographic printing plate precursor inthe present invention can be performed according to standard methods ata temperature of 0 to 60° C., preferably 15 to 40° C. or so, byimmersing the exposed lithographic printing plate precursor in adeveloper and wiping it with a brush, or by spraying it with a developerand wiping it with a brush or the like, for example.

The development with a developer containing a surfactant in the presentinvention can be conveniently performed in an automatic developingmachine equipped with a developer feeding means and a wiping member. Anautomatic developing machine using a rotating brush roll as a wipingmeans is especially preferred. Further, the automatic developing machinepreferably comprises a means for removing an excess of the developersuch as a squeeze roller or a drying means such as a hot-air heaterdownstream of the developing means. Further, the automatic developingmachine may comprise a preheating means for heating the image-exposedlithographic printing plate precursor upstream of the developing means.

Examples of automatic developing machines used in the process forpreparing a lithographic printing plate of the present invention are thesame as described for the first embodiment.

The developer used for the developer process in the present inventioncontains a surfactant. The developer is preferably an aqueous solutioncontaining a major proportion of water (containing 60% by mass or moreof water) Especially, it is preferably an aqueous solution containing asurfactant (anionic, nonionic, cationic, zwitterionic or the like) at pH2.0 to 10.0 or an aqueous solution containing a water-soluble polymercompound. Also, it is preferably an aqueous solution containing bothsurfactant and water-soluble polymer compound. The pH of the developeris more preferably 3.5 to 10.0, even more preferably 6 to 10.0,especially preferably 6.5 to 10.0. Especially in the method using adeveloper at pH 2.0 to 10.0, it is very difficult to satisfy stainingresistance, printing durability, and developability simultaneously. Thereason for this can be explained as follows. When the same material fora lithographic printing plate precursor is used with varying types ofdevelopers, developability and staining resistance in unexposed areasdeteriorate with developers at pH 2.0 to 10.0 as compared withconventional alkaline developers at pH 12 to 13. If the hydrophilicityof the material is increased to improve developability and stainingresistance with developers at pH 2.0 to 10.0, printing durability tendsto deteriorate. However, such developers at pH 2.0 to 10.0 canconveniently be used by employing the lithographic printing plateprecursor of the present invention.

Examples of surfactants used in the developer in the present inventioninclude the cationic surfactants, nonionic surfactants and zwitterionicsurfactants described in the first embodiment and also cover the samepreferred ranges.

Two or more of the surfactants may be used in the developer. The amountof the surfactants contained in the developer is preferably 0.01 to 20%by mass, more preferably 0.1 to 10% by mass.

Details of the water-soluble polymer compound used in the developer inthe present invention can be found in the description of the firstembodiment.

The developer used in the present invention may contain a pH bufferingagent. Details of the pH buffering agent can be found in the descriptionof the first embodiment.

In the present invention, the developer may contain an organic solvent.Details of the organic solvent can be found in the description of thefirst embodiment.

In the present invention, the developer may contain preservatives,chelating compounds, defoamers, organic acids, inorganic acids,inorganic salts and the like in addition to the components mentionedabove. Specifically, the compounds described in paragraphs [0266] to[0270] of JP-A2007-206217 can preferably be used.

In the present invention, the developer can be used as a developer and areplenishment developer for the exposed lithographic printing plateprecursor. Further, it can preferably be applied to the automaticdeveloping machine as described above. In the case of development usingan automatic developing machine, the developer fatigues with the numberof cycles so that the throughput may be recovered by using thereplenishment developer or a fresh developer.

(Miscellaneous)

In the process for preparing a lithographic printing plate from thelithographic printing plate precursor of the present invention, thelithographic printing plate precursor may be totally heated beforeexposure, during exposure or between exposure and development, ifdesired. Such heating may promote image-forming reaction in thephotosensitive layer, leading to benefits such as improvements inprinting durability and stabilization of sensitivity. In the case of thedeveloper process, the overall postheating or overall exposure of thedeveloped image is also effective to improve image fastness and printingdurability. Typically, heating before development preferably takes placeunder mild conditions of 150° C. or less. If the temperature is toohigh, non-image areas may be hardened or other problems may occur.Heating after development takes place under very vigorous conditions,typically in the range of 100 to 500° C. If the temperature is low,sufficient effect on image fastness cannot be obtained, but if it is toohigh, such problems as substrate degradation or thermal degradation ofimage areas may occur.

Features of the present invention will further be detailed referring toExamples. Note that the amount of use, ratio, details of processes, andprocedures of processes described in Examples below may be arbitrarilymodified, without departing from the spirit of the present invention.The scope of the present invention is, therefore, not restrictivelyunderstood by the specific examples described below.

Example A Synthesis Example of Copolymers 1 <Synthesis of SpecificPolymer Compound P-1-4>

A 500-ml three-neck flask was charged with 1.98 g ofdimethyl-N-methacryloyloxyethyl-N-carboxymethyl-ammonium betaine (fromOsaka Organic Chemical Industry Ltd.), 9.68 g of 2-(phosphonooxy)ethylmethacrylate (from Kyoeisha Chemical Co., Ltd.), 8.34 g of2-methacrylamide ethylamine (synthetic product), and 40 g of distilledwater, and the mixture was heated with stirring for 10 minutes at 60° C.under a stream of nitrogen gas. Then, 0.9 g of the polymerizationinitiator VA-046B (from Wako Pure Chemical Industries, Ltd.) wasdissolved in 40 g of distilled water, and added dropwise over 3 hours.Then, 0.9 g of VA-046B was added again, and the mixture was heated at80° C. for 3 hours, and then cooled.The resulting polymer solution was adjusted to pH 9.7 by adding NaOH.Then, 0.2 g of 4-OH TEMPO (from Tokyo Chemical Industry Co., Ltd.) wasadded, and the mixture was heated to 55° C., and 30.22 g of methacrylicanhydride (from Aldrich) was added dropwise over 1 hour. Aftercompletion of the dropwise addition, the mixture was kept at 55° C. for6 hours. Then, 500 g of ethyl acetate was added, and the lower layer wascollected. To the collected lower layer was added 15 g of the ionexchange resin Amberlyst R15 (from Aldrich), and the mixture was stirredat room temperature for 2 hours, and then Amberlyst R15 was removed byfiltration to give an aqueous solution of specific polymer compoundP-1-4. The weight average molecular weight (Mw) of the resultingspecific polymer compound P-1-4 was determined to be 120,000 by GelPermeation Chromatography (GPC) using polyethylene glycol as standard.

<Synthesis of Specific Polymer Compound P-1-54>

A 500-ml three-neck flask was charged with4-((3-methacrylamidepropyl)dimethylammonio)butane-1-sulfonate (5.17 g),vinylphosphonic acid (from BASF) (4.53 g), an aqueous solution of 15.0%by weight ofN-(3-(2-(2-(3-aminopropoxy)ethoxy)ethoxy)propyl)methacrylamidemonophosphate (23.5 g), and distilled water (30 g), and the mixture washeated with stirring for 10 minutes at 60° C. under a stream of nitrogengas. Then, the polymerization initiator VA-046B (from Wako Pure ChemicalIndustries, Ltd.) (0.3 g) was dissolved in distilled water (20 g), andadded dropwise over 3 hours. Then, VA-046B (0.3 g) was added again, andthe mixture was heated at 80° C. for hours, and then cooled.The resulting polymer solution was adjusted to pH 9.7 by adding NaOH.Then, 0.1 g of 4-OH TEMPO (from Tokyo Chemical Industry Co., Ltd.) wasadded, and the mixture was heated to 55° C., and methacrylic anhydride(from Aldrich) (10.0 g) was added dropwise over 1 hour. After completionof the dropwise addition, the mixture was kept at 55° C. for 6 hours.Then, ethyl acetate (250 g) was added, and the lower layer wascollected. To the collected lower layer was added 15 g of the ionexchange resin Amberlyst R15 (from Aldrich), and the mixture was stirredat room temperature for 2 hours, and then Amberlyst R15 was removed byfiltration to give an aqueous solution of specific polymer compoundP-1-54. The weight average molecular weight (Mw) of the resultingspecific polymer compound P-1-4 was determined to be 10,000 by GelPermeation Chromatography (GPC) using polyethylene glycol as standard.Other specific polymer compounds of the present invention were alsosynthesized in the same manner except that the monomer components of therepeating unit in the synthesis example above were changed, the type andamount of the reactive reagent used in the amino substitution reactionand that an existing synthesis method was used, if desired.

Example B Lithographic Printing Plates (1) Preparation of LithographicPrinting Plate Precursors [Preparation of Aluminum Substrate 1]

An aluminum plate having a thickness of 0.3 mm (quality: JIS A1050) wasdegreased using an aqueous solution of 10% by mass of sodium aluminateat 50° C. for 30 seconds to remove the rolling oil on the surface, andthen grained on the aluminum surface using three nylon brushescontaining bunches of bristles having a diameter of 0.3 mm and anaqueous suspension of a pumice having a median diameter of 25 μm(specific gravity 1.1 g/cm³), and thoroughly washed with water. Thisplate was etched by immersion in an aqueous solution of 25% by mass ofsodium hydroxide at 45° C. for seconds, and washed with water, and thenfurther immersed in an aqueous solution of 20% by mass of nitric acidfor seconds at 60° C., and washed with water. The amount of the grainedsurface etched here was about 3 g/m².

Then, the plate was continuously subjected to an electrochemicalsurface-roughening treatment using 60 Hz AC voltage. The electrolyte wasan aqueous solution of 1% by mass of nitric acid (containing 0.5% bymass of aluminum ions) at a temperature of 50° C. The electrochemicalsurface-roughening treatment took place using a carbon electrode as acounter electrode with an AC power supply generating a trapezoidal wave,TP (the time until the current value reaches a peak from zero)=0.8 msec,duty ratio 1:1. An auxiliary ferrite anode was used. The peak currentdensity was 30 A/dm², and 5% of the current from the power supply wasshunted to the auxiliary anode.

The quantity of electricity in the electrolysis in nitric acid was 175C/dm² when the aluminum plate was used as a cathode.Then, the plate was washed with water by spraying.

Then, the plate was subjected to an electrochemical surface-rougheningtreatment in the same manner as the electrolysis in nitric acid exceptthat an aqueous solution of 0.5% by mass of hydrochloric acid(containing 0.5% by mass of aluminum ions) was used as an electrolyte ata temperature of 50° C. and the quantity of electricity was C/dm² whenthe aluminum plate was used as a cathode, and then the plate was washedwith water by spraying. This aluminum plate was treated in an aqueoussolution of 15% by mass of sulfuric acid (containing 0.5% by mass ofaluminum ions) as an electrolyte at a current density of 15 A/dm² toform an anodic oxide coating of 2.5 g/m² using a DC power supply, thenwashed with water, and dried to prepare aluminum substrate 1.

The center line average roughness (Ra) of the substrate obtained in thismanner was determined to be 0.51 μm using a needle having a diameter of2 μm.

[Preparation of Aluminum Substrate 2]

The aluminum substrate 1 was treated in an aqueous solution of 1% bymass of sodium silicate at 20° C. for 10 seconds to prepare aluminumsubstrate 2. The surface roughness was determined to be 0.54 μm(expressed as Ra according to JIS B0601).

[Preparation of Aluminum Substrate 3]

An aluminum plate having a thickness of 0.24 mm (quality 1050, temperdesignation H16) was degreased by immersion in a 5% aqueous sodiumhydroxide solution kept at 65° C. for 1 minute, and then washed withwater. This aluminum plate was neutralized by immersion in a 10% aqueoushydrochloric acid solution kept at 25° C. for 1 minute, and then washedwith water. Then, this aluminum plate was surface-roughened by AC in anaqueous solution of 0.3% by mass of hydrochloric acid at 25° C. underthe conditions of a current density of 100 A/dm² for 60 seconds, andthen desmutted in a 5% aqueous sodium hydroxide solution kept at 60° C.for 10 seconds. This aluminum plate was subjected to an anodic oxidationtreatment in a 1.5% aqueous sulfuric acid solution at 25° C. underconditions of a current density of 10 A/dm² and voltage 15 V for 1minute to prepare an aluminum substrate. The surface roughness wasdetermined to be 0.44 μm (expressed as Ra according to JIS B0601).

[Formation of Primer Layer 1]

On the aluminum substrates 1 to 3, a coating solution for primer layer 1having the composition shown below was applied using a bar coater, anddried at 100° C. for 1 minute to form primer layer 1. The coating massof primer layer 1 was 12 mg/m² after drying.

<Coating Solution for Primer Layer 1>

One of the specific polymer compounds described in 0.50 g Table 1 andTable 2 or the polymer compounds for comparison shown below Methanol90.0 g Pure water 10.0 g

[Formation of Photosensitive Layer 1-1]

A coating solution for photosensitive layer 1-1 having the compositionshown below was applied on the primer layer 1 using a bar coater, andthen dried in an oven at 90° C. for seconds to form photosensitive layer1-1 having a coating mass of 1.3 g/m² after drying.

<Coating Solution for Photosensitive Layer 1-1>

Binder polymer (1) shown below (mass average molecular 0.34 g weight:80,000) Polymerizable compound (1) shown below 0.68 g (PLEX6661-O fromDegussa Japan Co., Ltd.) Sensitizing dye (1) shown below 0.06 gPolymerization initiator (1) shown below 0.18 g Chain transfer agent (1)shown below 0.02 g Dispersion of ε-phthalocyanine pigment 0.40 g(pigment: 15 parts by mass, dispersant (allyl methacrylate/ methacrylicacid copolymer (mass average molecular weight: 60,000, molar ratio:83/17)): 10 parts by mass, cyclohexanone: 15 parts by mass) Thermalpolymerization inhibitor 0.01 g (N-nitrosophenylhydroxylamine aluminumsalt) Fluorosurfactant (1) shown below (mass average molecular 0.001 gweight: 10,000) Polyoxyethylene-polyoxypropylene condensate 0.02 g(Pluronic L44 from ADEKA) Dispersion of yellow pigment 0.04 g (yellowpigment Novoperm Yellow H2G (from Clariant): 15 parts by mass,dispersant (allylmethacrylate/methacrylic acid copolymer (mass averagemolecular weight: 60,000, molar ratio: 83/17)): 10 parts by mass,cyclohexanone: 15 parts by mass) 1-Methoxy-2-propanol 3.5 g Methyl ethylketone 8.0 g Binder polymer (1)

Polymerizable compound (1)

Sensitizing dye (1)

Polymerization initiator (1)

Chain transfer agent (1)

Fluorosurfactant (1)

[Formation of Photosensitive Layer 1-2]

A coating solution for photosensitive layer 1-2 having the compositionshown below was applied on the primer layer using a bar coater, and thendried in an oven at 90° C. for 60 seconds to form photosensitive layer1-2 having a coating mass of 1.3 g/m² after drying.

<Coating Solution for Photosensitive Layer 1-2>

Binder polymer (1) shown above (mass average molecular 0.04 g weight:50,000) Binder polymer (2) shown below (mass average molecular 0.30 gweight: 80,000) Polymerizable compound (1) shown above 0.17 gPolymerizable compound (2) shown below 0.51 g Sensitizing dye (2) shownbelow 0.03 g Sensitizing dye (3) shown below 0.015 g Sensitizing dye (4)shown below 0.015 g Polymerization initiator (1) shown above 0.13 gChain transfer agent: mercaptobenzothiazole 0.01 g Dispersion ofε-phthalocyanine pigment 0.40 g (pigment: 15 parts by mass, dispersant(allyl methacrylate/ methacrylic acid copolymer (mass average molecularweight: 60,000, molar ratio: 83/17)): 10 parts by mass, cyclohexanone:15 parts by mass) Thermal polymerization inhibitor 0.01 g(N-nitrosophenylhydroxylamine aluminum salt) Fluorosurfactant (1) shownabove (mass average molecular 0.001 g weight: 10,000)1-Methoxy-2-propanol 3.5 g Methyl ethyl ketone 8.0 g

Sensitizing dye (2)

Sensitizing dye (3)

Sensitizing dye (4)

[Formation of Photosensitive Layer 1-3]

A coating solution for photosensitive layer 1-3 having the compositionshown below was applied on the primer layer using a bar coater, and thendried in an oven at 100° C. for 60 seconds to form photosensitive layer1-3 having a coating mass of 1.0 g/m² after drying. The coating solutionfor photosensitive layer 1-3 was prepared by mixing the sensitizersolution (1) and hydrophobizing solution (1) shown below and stirringthe mixture immediately before it was applied.

<Sensitizer Solution (1)>

Binder polymer (3) shown below 0.162 g IR absorber (1) shown below 0.030g Polymerization initiator (3) shown below 0.162 g Polymerizablecompound (ARONIX M215 from Toagosei 0.385 g Co., Ltd.) PIONIN A-20 (fromTAKEMOTO OIL & FAT Co., Ltd.) 0.055 g Oil-sensitizer (1) shown below0.044 g Fluorosurfactant (1) shown above 0.008 g Methyl ethyl ketone1.091 g 1-Methoxy-2-propanol 8.609 g

<Hydrophobizing Solution (1)>

Aqueous dispersion of hydrophobization precursor (1) shown 2.640 g belowDistilled water 2.425 g

(Preparation of an Aqueous Dispersion of Hydrophobization Precursor (1))

A 1000-ml four-neck flask equipped with a stirrer, a thermometer, adropping funnel, a nitrogen inlet, and a reflux condenser was chargedwith 350 mL of distilled water under deoxygenation by nitrogen gaspurging and heated until the internal temperature reached 80° C. To thiswere added 1.5 g of sodium dodecylsulfate as a dispersant, and 0.45 g ofammonium persulfide as an initiator, and then a mixture of 45.0 g ofglycidyl methacrylate and 45.0 g of styrene was added dropwise via thedropping funnel over about one hour. After completion of the dropwiseaddition, the reaction was continued for 5 hours, and then unreactedmonomers were removed by steam distillation. Then, the mixture wascooled and adjusted to pH 6 with aqueous ammonia, and finally pure waterwas added to reduce non-volatiles to 15% by mass, thereby giving anaqueous dispersion of hydrophobization precursor (1) consisting ofpolymer microparticles. The particle size distribution of the polymermicroparticles had a maximum at a particle size of nm.

The particle size distribution was determined by taking an electronmicrograph of the polymer microparticles and measuring the particle sizeof a total of 5000 microparticles on the photograph, and plotting thefrequency of appearance of each of 50 particle sizes on a logarithmicscale from the maximum to zero of the measured particle sizes. Theparticle sizes of nonspherical particles were determined as the particlesizes of spherical particles having the same particle areas on thephotograph.

[Formation of Protective Layer 1]

A coating solution for protective layer 1 having the composition shownbelow was applied using a bar coater at a coating mass of 0.75 g/m²after drying, and then dried at 125° C. for 70 seconds to formprotective layer 1.

<Coating Solution for Protective Layer 1>

Polyvinyl alcohol (degree of saponification: 98 mol %, 40 g degree ofpolymerization: 500) Polyvinylpyrrolidone (molecular weight: 50,000) 5 gPoly[vinylpyrrolidone/vinyl acetate (1/1)] (molecular 0.5 g weight:70,000) Surfactant (EMALEX 710 from Nihon Emulsion Co., Ltd.) 0.5 gWater 950 g

[Formation of Protective Layer 2]

A coating solution for protective layer 2 having the composition shownbelow was applied using a bar coater at a coating mass of 0.75 g/m²after drying, and then dried at 125° C. for 70 seconds to formprotective layer 2.

Coating Solution for Protective Layer 2>

Dispersion of inorganic laminar compound (1) described  1.5 g belowAqueous solution of 6% by mass of sulfonic acid-modified 0.55 gpolyvinyl alcohol (CKS50 from The Nippon Synthetic Chemical IndustryCo., Ltd.; degree of saponification 99 mol % or more, degree ofpolymerization 300) Aqueous solution of 6% by mass of polyvinyl alcohol0.03 g (PVA-405 from KURARY CO., LTD.; degree of saponification 81.5 mol%, degree of polymerization 500, a 6% by mass aqueous solution) Aqueoussolution of 1% by mass of a surfactant 0.86 g (EMALEX 710 from NihonEmulsion Co., Ltd.) Ion exchange water  6.0 g

(Preparation of a Dispersion of Inorganic Laminar Compound (1))

To 193.6 g of ion exchange water was added 6.4 g of synthetic micaSomasif ME-100 (from Co-op Chemical Co., Ltd.), and the mixture wasdispersed using a homogenizer until the average particle size (by laserscattering) reached 3 μm to prepare a dispersion of inorganic laminarcompound (1). The resulting dispersed particles had an aspect ratio ofor more.

The aluminum substrates, copolymers (A) added to primer layer 1, coatingsolutions for photosensitive layer, and coating solutions for protectivelayer described above were combined as shown in Table 1 and Table 2 toprepare lithographic printing plate precursors A-1-1 to A-1-77, andB-1-1 to B-1-10.

TABLE 1 Coating liquid Coating liquid Lithographic Specific for formingfor forming printing plate Aluminum polymer image recording protectiveprecursor support compound layer layer A-1-1 1 P-1-1 1-1 1 A-1-2 1 P-1-21-1 1 A-1-3 1 P-1-3 1-1 1 A-1-4 1 P-1-4 1-1 1 A-1-5 1 P-1-5 1-1 1 A-1-61 P-1-6 1-1 1 A-1-7 1 P-1-7 1-1 1 A-1-8 1 P-1-8 1-1 1 A-1-9 1 P-1-9 1-11 A-1-10 1 P-1-10 1-1 1 A-1-11 1 P-1-9 1-1(*) 1 A-1-12 1 P-1-10 1-1(*) 1A-1-13 1 P-1-12 1-1 1 A-1-14 1 P-1-13 1-1 1 A-1-15 1 P-1-14 1-1 1 A-1-161 P-1-16 1-1 1 A-1-17 1 P-1-18 1-1 1 A-1-18 1 P-1-20 1-1 1 A-1-19 1P-1-22 1-1 1 A-1-20 1 P-1-23 1-1 1 A-1-21 1 P-1-24 1-1 1 A-1-22 1 P-1-251-1 1 A-1-23 1 P-1-26 1-1 1 A-1-24 1 P-1-27 1-1 1 A-1-25 1 P-1-28 1-1 1A-1-26 1 P-1-29 1-1 1 A-1-27 1 P-1-30 1-1 1 A-1-28 1 P-1-31 1-1 1 A-1-291 P-1-32 1-1 1 A-1-30 1 P-1-33 1-1 1 A-1-31 1 P-1-34 1-1 1 A-1-32 1P-1-35 1-1 1 A-1-33 1 P-1-37 1-1 1 A-1-34 1 P-1-39 1-1 1 A-1-35 1 P-1-401-1 1 A-1-36 1 P-1-41 1-1 1 A-1-37 1 P-1-42 1-1 1 A-1-38 1 P-1-43 1-1 1A-1-39 1 P-1-44 1-1 1 A-1-40 1 P-1-45 1-1 1 A-1-41 1 P-1-46 1-1 1 A-1-421 P-1-47 1-1 1 A-1-43 1 P-1-50 1-1 1 A-1-66 1 P-1-51 1-1 1 A-1-67 1P-1-52 1-1 1 A-1-68 1 P-1-53 1-1 1 A-1-69 1 P-1-54 1-1 1 A-1-70 1 P-1-551-1 1 A-1-71 1 P-1-56 1-1 1 (*)1: No primer layer was applied, but aphotosensitive layer was formed by mixing a coating solution for primerlayer containing a specific polymer compound with a coating solution forphotosensitive layer immediately before it was applied.

TABLE 2 Coating liquid Coating liquid Lithographic Specific for formingfor forming printing plate Aluminum polymer image recording protectiveprecursor support compound layer layer A-1-44 3 P-1-9 1-2 1 A-1-45 3P-1-10 1-2 1 A-1-46 3 P-1-12 1-2 1 A-1-47 3 P-1-20 1-2 1 A-1-48 3 P-1-261-2 1 A-1-49 3 P-1-28 1-2 1 A-1-50 3 P-1-37 1-2 1 A-1-51 3 P-1-39 1-2 1A-1-52 3 P-1-41 1-2 1 A-1-53 3 P-1-44 1-2 1 A-1-54 3 P-1-46 1-2 1 A-1-552 P-1-9 1-3 2 A-1-56 2 P-1-10 1-3 2 A-1-57 2 P-1-12 1-3 2 A-1-58 2P-1-20 1-3 2 A-1-59 2 P-1-26 1-3 2 A-1-60 2 P-1-28 1-3 2 A-1-61 2 P-1-371-3 2 A-1-62 2 P-1-39 1-3 2 A-1-63 2 P-1-41 1-3 2 A-1-64 2 P-1-44 1-3 2A-1-65 2 P-1-46 1-3 2 A-1-72 3 P-1-53 1-2 1 A-1-73 3 P-1-54 1-2 1 A-1-743 P-1-55 1-2 1 A-1-75 2 P-1-53 1-3 2 A-1-76 2 P-1-54 1-3 2 A-1-77 2P-1-55 1-3 2 B-1-1 1 R-1-1 1-1 1 B-1-2 1 R-1-2 1-1 1 B-1-3 1 R-1-3 1-1 1B-1-4 1 R-1-4 1-1 1 B-1-5 1 R-1-5 1-1 1 B-1-6 3 R-1-2 1-2 1 B-1-7 3R-1-4 1-2 1 B-1-8 3 R-1-5 1-2 1 B-1-9 2 R-1-4 1-3 2 B-1-10 2 R-1-5 1-3 2

In Table 1 and Table 2, specific polymer compounds P-1-1 to P-1-56represent specific examples of copolymers (A) of the present invention.The polymer compounds R-1-1 to R-1-5 for comparative examples used inlithographic printing plate precursors B-1-1 to B-1-10 are compounds forcomparison having structures shown below.

(2) Evaluation of Lithographic Printing Plate Precursors

[Exposure, Development and Printing]

Various lithographic printing plate precursors shown in Tables 3 to 5below were image-exposed using Violet semiconductor laser platesetterVx9600 (incorporating an InGaN semiconductor laser (emission wavelength405 nm±10 nm/output 30 mW)) from FUJIFILM Electronic Imaging Ltd.(FFEI). The image exposure was performed using an FM screen (TAFFETA 20)from Fujifilm Corporation at a resolution of 2,438 dpi and a surfaceexposure dose of 0.05 mJ/cm² to attain a dot area fraction of 50%.Then, the plate precursors were preheated at 100° C. for 30 seconds, andthen developed using each developer shown below in an automaticdeveloping machine having a structure as shown in FIG. 1. The automaticdeveloping machine was provided with one brush roll of 50 mm in outsidediameter including polybutylene terephthalate bristles (bristle diameter200 μm, bristle length 17 mm) and rotated in the same direction as thefeed direction at 200 rpm (a peripheral speed of 0.52 m/sec at the endof the brush). The temperature of the developer was 30° C. Thelithographic printing plate precursors were fed at a feed speed of 100cm/min. The development was followed by drying in a drying part. Thedrying temperature was 80° C. When developer 2 was used, the dryingafter development was preceded by washing with water.

The compositions of developers 1 to 5 are shown below. In thecompositions below, Newcol B13 (from NIPPON NYUKAZAI CO., LTD.) ispolyoxyethylene β-nephthyl ether (average number of oxyethylene groupsn=13), and gum arabic has a mass average molecular weight of 200,000.

Developer 1>

Sodium carbonate 13. 0 g Sodium hydrogen carbonate 7.0 g Newcol B13 50.0g Ammonium phosphate monobasic 2.0 g 2-Bromo-2-nitropropane-1,3-diol0.01 g 2-Methyl-4-isothiazolin-3-one 0.01 g Trisodium citrate 15.0 gDistilled water (pH: 9.8) 913.98 g

Developer 2>

Potassium hydroxide 0.15 g Newcol B13 5.0 g Chelest 400 (chelatingagent) 0.1 g Distilled water (pH: 12.05 94.75 g

Developer 3>

Gum arabic 25.0 g Enzymatically modified potato starch 70.0 g Sodiumsalt of dioctyl sulfosuccinic acid ester 5.0 g Ammonium phosphatemonobasic 1.0 g Citric acid 1.0 g 2-Bromo-2-nitropropane-1,3-diol 0.01 g2-Methyl-4-isothiazolin-3-one 0.01 g Zwitterionic surfactant shown below(compound W-1) 70.0 g Anionic surfactant shown below (compound AN-1) 3.0g Distilled water 824.98 g (adjusted to pH 4.5 with phosphoric acid andsodium hydroxide)

<Developer 4>

Water 937.2 g Anionic surfactant shown below (compound W-2) 23.8 gPhosphoric acid 3 g Phenoxypropanol 5 g Triethanolamine 6 g Potatodextrin 25 g

<Developer 5>

Water 88.6 g Nonionic surfactant shown below (W-3) 2.4 g Nonionicsurfactant shown below (W-4) 2.4 g Nonionic surfactant 1.0 g (EMALEX 710from Nihon Emulsion Co., Ltd.) Phenoxypropanol 1.0 g Octanol 0.6 gN-(2-hydroxyethyl)morpholine 1.0 g Triethanolamine 0.5 g Sodiumgluconate 1.0 g Trisodium citrate 0.5 g Tetrasodiumethylenediaminetetraacetate 0.05 g Polystyrene sulfonate 1.0 g (VersaTL77 (a 30% solution) from Alco Chemical) (adjusted to pH 7.0 withphosphoric acid)

The lithographic printing plates obtained were mounted on the printingpress SOR-M from Heidelberg Printing Machines AG to perform printingwith a dampening water (EU-3 (an etching solution from FujifilmCorporation)/water/isopropyl alcohol=1/89/10 (volume ratio)) andTRANS-G(N) black ink (from DIC Corporation) at a printing speed of 6000sheets/hr.

[Evaluation]

Each lithographic printing plate precursor was evaluated for printingdurability, staining resistance, staining resistance over time anddevelopability as follows. The results are shown in Tables 3 to 5.

<Printing Durability>

As the number of prints increased, the ink density on printing paperdecreased because the photosensitive layer gradually wore and decreasedin ink receptivity. In printing plates exposed at the same exposuredose, printing durability was evaluated by determining the number ofprints when the ink density (reflection density) decreased by 0.1 ascompared with the density at the start of printing. The evaluation ofprinting durability was reported as the relative printing durabilitydefined below using Comparative examples 1-1, 1-7 and 1-10 as references(1.0) respectively in Tables 3 to 5. Higher values of the relativeprinting durability indicate higher printing durability. Relativeprinting durability=(Printing durability of test lithographic printingplate precursor)/(Printing durability of reference lithographic printingplate precursor).

<Staining Resistance>

After printing was started, the 20th print was sampled to evaluatestaining resistance by the density of the ink deposited on non-imageareas. The ink deposition on non-image areas was reported as a score ofvisual evaluation per 75 cm² because it does not always occur uniformly.Scores of visual evaluation for ink-deposited area fractions innon-image areas are as follows: score 10 for 0%, score 9 for more than0% and 10% or less, score 8 for more than 10% and 20% or less, score 7for more than 20% and 30% or less, score 6 for more than 30% and 40% orless, score 5 for more than 40% and 50% or less, score for more than 50%and 60% or less, score 3 for more than 60% and 70% or less, score 2 formore than 70% and 80% or less, score 1 for more than 80% and 90% orless, and score 0 for more than 90% and 100% or less. Higher scoresindicate better staining resistance.

<Staining Resistance Over Time>

After the lithographic printing plate was prepared, it was left in aconstant temperature and humidity chamber set at 60° C. and a relativehumidity of 60% for three days. This printing plate was used to evaluatestaining resistance over time in the same manner as described for theevaluation of staining resistance. Higher scores indicate betterstaining resistance over time.

<Developability>

The development process described above was performed at varying feedspeeds, and the cyan density in non-image areas of the resultinglithographic printing plate was measured by a MacBeth densitometer.Developability was evaluated by determining the feed speed when the cyandensity in non-image areas equaled to the cyan density in the aluminumsubstrate. The evaluation of developability was reported as the relativedevelopability defined below using Comparative examples 1-1, 1-7 and1-10 as references (1.0) respectively in Tables 3 to 5. Higher values ofthe relative developability indicate higher developability and betterperformance.

Relative developability=(Feed speed of test lithographic printing plateprecursor)/(Feed speed of reference lithographic printing plateprecursor)

TABLE 3 Lithographic Printing performance printing Printing StainingStraining resistance plate precursor Developer durability resistanceover time Developability Example 1-1 A-1-1  1 1.9

7 1.2 Example 1-2 A-1-2  1 2.0

7 1.2 Example 1-3 A-1-3  1 1.6

8 1.2 Example 1-4 A-1-4  1 1.7

8 1.2 Example 1-5 A-1-5  1

9 9 1.2 Example 1-6 A-1-6  1 1.7 9 9 1.2 Example 1-7 A-1-7  1 1.6 10 101.0 Example 1-8 A-1-8  1

10 9 1.0 Example 1-9 A-1-9  1 1.6 10 10 1.2 Example 1-10 A-1-10 1 1.7 109 1.2 Example 1-11 A-1-10 3

10 9 1.0 Example 1-12 A-1-10 4 1.7 10 9 1.0 Example 1-13 A-1-10 5 1.7 109 1.0 Example 1-14 A-1-11 1 1.6 10 10 1.1 Example 1-15 A-1-12 1 1.7 1010 1.1 Example 1-16 A-1-13 1

9 9 1.3 Example 1-17 A-1-14 1 1.6 9 9 1.2 Example 1-18 A-1-15 1 1.7 9 81.2 Example 1-19 A-1-16 1

9 8 1.1 Example 1-20 A-1-17 1 1.9 9 8 1.1 Example 1-21 A-1-18 1 2.0 8 81.1 Example 1-22 A-1-19 1 2.1 8 8 1.1 Example 1-23 A-1-20 1 1.7 9 9 1.1Example 1-24 A-1-21 1 1.7 9 8 1.1 Example 1-25 A-1-22 1 1.7 8 8 1.1Example 1-26 A-1-23 1 1.9 8 7 1.1 Example 1-27 A-1-24 1 1.7 8 8 1.1Example 1-28 A-1-25 1 1.8 9 8 1.1 Example 1-29 A-1-26 1 1.8 8 8 1.1Example 1-30 A-1-27 1 1.7 8 8 1.1 Example 1-31 A-1-28 1 1.9 7 7 1.1Example 1-32 A-1-29 1 2.4 8 7 1.1 Example 1-33 A-1-30 1 1.6 9 9 1.1Example 1-34 A-1-31 1 1.7 10 9 1.2 Example 1-35 A-1-32 1 1.7 10 9 1.2Example 1-36 A-1-33 1 2.1 9 8 1.0 Example 1-37 A-1-34 1 2.2 9 8 1.0Example 1-38 A-1-35 1

8 8 1.0 Example 1-39 A-1-36 1

8 8 1.0 Example 1-40 A-1-37 1

8 8 1.0 Example 1-41 A-1-38 1

8 8 1.0 Example 1-42 A-1-39 1

8 8 1.1 Example 1-43 A-1-40 1

7 7 1.1 Example 1-44 A-1-41 1 1.6 8 8 1.1 Example 1-45 A-1-42 1

7 7 1.0 Example 1-46 A-1-43 1 1.8 7 6 1.0 Example 1-104 A-1-44 1 2.1 9 91.1 Example 1-105 A-1-67 1 2.0 9 9 1.1 Example 1-106 A-1-68 1 2.0 8 81.3 Example 1-107 A-1-69 1 1.9 10 10 1.1 Example 1-108 A-1-70 1 2.0 8 81.0 Example 1-109 A-1-71 1 2.0 8 8 1.0 Comparative B-1-1  1 1.0 3 3 1.0Example 1-1 Comparative B-1-2  1 1.1 2 2 0.9 Example 1-2 ComparativeB-1-3  1 1.2 4 4 1.0 Example 1-3 Comparative B-1-4  1 0.6 5 5 1.0Example 1-4 Comparative B-1-5  1 1.0 5 4 0.5 Example 1-5 Comparative — 10.8 0 0 0.2 Example 1-6

indicates data missing or illegible when filed

TABLE 4 Printing performance Stain- Litho- ing graphic Print- Stain-resis- printing ing ing tance plate Devel- dura- resis- over Devel-precursor oper bility tance time opability Example 1-47 A-1-9 2

10 10 1.4 Example 1-48 A-1-10 2 1.7 10 9 1.4 Example 1-49 A-1-13 2

8 1.6 Example 1-50 A-1-18 2 2.0 8 8 1.4 Example 1-51 A-1-23 2

8 7 1.4 Example 1-52 A-1-25 2

9 8 1.3 Example 1-53 A-1-33 2

9 8 1.1 Example 1-54 A-1-34 2 2.0 9 9 1.1 Example 1-55 A-1-36 2

9 9 1.1 Example 1-56 A-1-39 2

7 7 1.1 Example 1-57 A-1-41 2

7 7 1.0 Example 1-110 A-1-68 2 2.0 8 8 1.5 Example 1-111 A-1-69 2

10 10 1.3 Example 1-112 A-1-70 2 2.0 8 7 1.2 Comparative B-1-2 2 1.0 4 21.0 Example 1-7 Comparative B-1-4 2 0.2 5 4 1.0 Example 1-8 ComparativeB-1-5 2 1.2 5 2

Example 1-9

indicates data missing or illegible when filed

TABLE 5 Printing performance Stain- Litho- ing graphic Print- Stain-resis- printing ing ing tance plate Devel- dura- resis- over Devel-precursor oper bility tance time opability Example 1-58 A-1-44 4 1.6 1010 1.3 Example 1-59 A-1-45 4 1.7 10 9

Example 1-60 A-1-45 1 1.7 10 9 1.3 Example 1-61 A-1-45 5 1.7 10 9 1.3Example 1-62 A-1-46 4 1.6 9 8 1.4 Example 1-63 A-1-47 4 1.9 8 8 1.3Example 1-64 A-1-48 4

8 7 1.3 Example 1-65 A-1-49 4

9 8 1.2 Example 1-66 A-1-50 4 1.8 9 8 1.1 Example 1-67 A-1-51 4 1.9 8 81.1 Example 1-68 A-1-52 4 1.6 8 8 1.0 Example 1-69 A-1-53 4 1.5 8 7 1.1Example 1-70 A-1-54 4 1.7 8 7 1.0 Example 1-113 A-1-72 4 1.9 8 8 1.4Example 1-114 A-1-73 4 1.9 10 10 1.2 Example 1-115 A-1-74 4 2.0 8 7 1.1Comparative B-1-6 4 1.0 3 2 1.0 Example 1-10 Comparative B-1-7 4 0.5 4 40.9 Example 1-11 Comparative B-1-8 4 1.1 4 2 1.0 Example 1-12

indicates data missing or illegible when filed

Tables 3 to 5 above show that Examples 1-1 to 1-70 and 1-104 to 1-115using copolymers (A) comprising repeating units complying with formula(a1-1) were excellent in staining resistance, staining resistance overtime and developability without compromising printing durability.However, Comparative example 1-1 using polymer compound R-1-1 forcomparative examples solely comprising a repeating unit having afunctional group interacting with the substrate surface and Comparativeexamples 1-2, 1-7, and 1-10 using polymer compound R-1-2 for comparativeexamples were all shown to be poor in printing durability, stainingresistance, and staining resistance over time. Comparative example 1-3using polymer compound R-1-3 for comparative examples comprising arepeating unit having a functional group interacting with the substratesurface and a side chain repeating unit having a polymerizable group ina side chain of the repeating unit but lacking a specific linking groupand not complying with formula (a1-1) was shown to be poor in stainingresistance and staining resistance over time.

Comparative examples 1-4, 1-8, and 1-11 using polymer compound R-1-4 forcomparative examples comprising a repeating unit having a functionalgroup interacting with the substrate surface and a repeating unitcontaining a hydrophilic group having a zwitterionic structure in a sidechain but lacking a polymerizable group in a side chain of any repeatingunit were all shown to be very poor in printing durability and also poorin the balance between staining resistance and staining resistance overtime.Comparative examples 1-5, 1-9, and 1-12 using polymer compound R-1-5 forcomparative examples comprising a repeating unit having a functionalgroup interacting with the substrate surface and a side chain repeatingunit having a polymerizable group in a side chain of the repeating unitbut lacking a specific linking group and not complying with formula(a1-1) were shown to be poor in staining resistance and stainingresistance over time.

<Exposure, Development and Printing>

Various lithographic printing plate precursors shown in Tables 6 and 7were image-exposed at a 50% tint using Trendsetter 3244VX from Creo(incorporating a water-cooled 40 W infrared semiconductor laser (830nm)) under conditions of an output power of 9 W, an external drumrotational speed of 210 rpm, and a resolution of 2,400 dpi. Then, theimage was developed using developer 1 or 4 in an automatic developingmachine having a structure shown in FIG. 2 with heater settings thatallow the plate surface to reach a temperature of 100° C. in thepreheating part and at a feed speed that allows an immersion time in thedeveloper (developing time) of 20 seconds.

The lithographic printing plates obtained were mounted on the printingpress SOR-M from Heidelberg Printing Machines AG to perform printingwith a dampening water (EU-3 (an etching solution from FujifilmCorporation)/water/isopropyl alcohol=1/89/10 (volume ratio)) andTRANS-G(N) black ink (from DIC Corporation) at a printing speed of 6000sheets/hr.

Each lithographic printing plate precursor was evaluated for printingdurability, staining resistance, staining resistance over time, anddevelopability in the same manner as in Example 1-1. The evaluation ofprinting durability and developability was made by using Comparativeexamples 1-13 and 1-15 as reference (1.0) in Tables 6 and 7,respectively. The results are shown in Tables 6 and 7.

TABLE 6 Printing performance Stain- Litho- ing graphic Print- Stain-resis- printing ing ing tance plate Devel- dura- resis- over Devel-precursor oper bility tance time opability Example 1-71 A-1-55 1 2.4 1010 1.4 Example 1-72 A-1-56 1 2.5 10 9 1.4 Example 1-73 A-1-57 1 2.3 9 91.6 Example 1-74 A-1-58 1 3.0 9 8 1.3 Example 1-75 A-1-59 1 2.5 8 8 1.3Example 1-76 A-1-60 1 2.4 9 9 1.2 Example 1-77 A-1-61 1 2.9 9 9 1.1Example 1-78 A-1-62 1 3.1 9 8 1.1 Example 1-79 A-1-63 1 2.6 8 7 1.1Example 1-80 A-1-64 1 2.1 8 7 1.1 Example 1-81 A-1-65 1 2.3 8 7 1.1Example 1-116 A-1-75 1 2.7 9 8 1.5 Example 1-117 A-1-76 1 2.7 10 10 1.3Example 1-118 A-1-77 1 2.8 8 7 1.2 Comparative B-1-9 1 1.0 4 4 1.0Example 1-13 Comparative B-1-10 1 1.8 4 1 1.0 Example 1-14

TABLE 7 Printing performance Stain- Litho- ing graphic Print- Stain-resis- printing ing ing tance plate Devel- dura- resis- over Devel-precursor oper bility tance time opability Example 1-82 A-1-55 4 2.3 1010 1.3 Example 1-83 A-1-56 4 2.4 10 9 1.3 Example 1-84 A-1-57 4 2.2 9 91.5 Example 1-85 A-1-58 4 2.9 9 8 1.2 Example 1-86 A-1-59 4 2.4 9 8 1.2Example 1-87 A-1-60 4 2.3 9 9 1.1 Example 1-88 A-1-61 4 2.8 9 8 1.1Example 1-89 A-1-62 4 2.9 9 8 1.1 Example 1-90 A-1-63 4 2.5 8 8 1.1Example 1-91 A-1-64 4 2.0 8 8 1.1 Example 1-92 A-1-65 4 2.2 8 7

Example 1-119 A-1-75 4 2.6 8 8 1.4 Example 1-120 A-1-76 4 2.6 10 10 1.2Example 1-121 A-1-77 4 2.7 8 7 1.1 Comparative B-1-9 4 1.0 3 3 1.0Example 1-15 Comparative B-1-10 4 1.4 3 1 0.8 Example 1-16

indicates data missing or illegible when filed

Tables 6 and 7 show that Examples 1-71 to 1-92 and 1-116 to 1-121 usingcopolymers (A) comprising repeating units complying with formula (a1-1)were excellent in staining resistance, staining resistance over time anddevelopability without compromising printing durability. However,Comparative examples 1-13 and 1-15 using polymer compound R-1-4 forcomparative examples comprising a repeating unit having a functionalgroup interacting with the substrate surface and a repeating unitcontaining a hydrophilic group having a zwitterionic structure in a sidechain but lacking a polymerizable group in a side chain of any repeatingunit were shown to be poor especially in staining resistance andstaining resistance over time. They also remained unsatisfactory inprinting durability and developability.

Comparative examples 1-14 and 1-16 using polymer compound R-1-5 forcomparative examples comprising a repeating unit having a functionalgroup interacting with the substrate surface and a repeating unit havinga polymerizable group in a side chain of the repeating unit but lackinga specific linking group and not complying with formula (a1-1) wereshown to be poor in staining resistance and staining resistance overtime. They also remained unsatisfactory in developability.

<Exposure, Development and Printing>

Various lithographic printing plate precursors shown in Table 8 belowwere exposed using Luxel PLATESETTER T-6000III incorporating an infraredsemiconductor laser from Fujifilm Corporation, under conditions of anexternal drum rotational speed of 1000 rpm, a laser output of 70%, and aresolution of 2400 dpi. The image formed by exposure included solidareas and halftone areas produced by 20 μm dot FM screening.The exposed lithographic printing plate precursors were mounted on theprinting press LITHRONE 26 from KOMORI Corporation without developingthe image. The image was developed on press with a dampening solution ofEcolity-2 (from Fujifilm Corporation)/tap water=2/98 (volume ratio) andValues-G(N) black ink (from DIC Corporation) by supplying the dampeningsolution and the ink according to the standard automatic print startingmode of LITHRONE 26, followed by printing on 100 sheets of Tokubishi Artpaper (76.5 kg) at a printing speed of 10000 sheets/hr.

[Evaluation]

Each lithographic printing plate precursor was evaluated for on-pressdevelopability and printing durability as follows. Staining resistanceand staining resistance over time were evaluated as described in Example1-1. The results are shown in Table below 8.

<On-Press Developability>

On-press developability was evaluated by determining the number ofsheets of printing paper required until on-press development ofnon-image areas of the photosensitive layer was completed and the inkwas no more transferred to the non-image areas.

<Printing Durability>

After the evaluation of on-press developability, printing was furthercontinued. As the number of prints increased, the ink density on theprints decreased because the photosensitive layer gradually wore.Printing durability was evaluated by determining the number of prints atthe end of printing when the dot area fraction of halftone dots producedby FM screening in a print measured by a Gretag densitometer decreasedby 5% as compared with the value measured in the 100th print. Theevaluation of printing durability was reported as the relative printingdurability defined below using Comparative example 1-17 as reference(1.0). Higher values of the relative printing durability indicate higherprinting durability.

Relative printing durability=(Printing durability of test lithographicprinting plate precursor)/(Printing durability of reference lithographicprinting plate precursor)

TABLE 8 Litho- graphic Printing performance printing Printing StainingStaining Number of plate dura- resis- resistance on-machine precursorbility tance overtime development Example 1-93 A-1-55 2.4 10 10 20Example 1-94 A-1-56 2.5 10 9 20 Example 1-95 A-1-57 2.2 9 8 5 Example1-96 A-1-58 2.8 9 8 30 Example 1-97 A-1-59 2.4 8 8 30 Example 1-98A-1-60 2.3 9 9 30 Example 1-99 A-1-61 2.7 9 8 35 Example 1-100 A-1-622.8 9 8 35 Example 1-101 A-1-63 2.4 8 7 35 Example 1-102 A-1-64 1.9 8 735 Example 1-103 A-1-65 2.2 8 7 40 Example 1-122 A-1-75 2.7 9 8 15Example 1-123 A-1-76 2.7 10 10 25 Example 1-124 A-1-77 2.8 8 7 30Comparative B-1-9 1.0 5 2 80 Example 1-17 Comparative B-1-10 1.3 3 2 200Example 1-18

Table 8 above shows that Examples 1-93 to 1-103 and 1-122 to 1-124 usingcopolymers (A) comprising a repeating unit complying with formula (a1-1)were excellent in staining resistance, staining resistance over time andon-press developability without compromising printing durability.

However, Comparative example 1-17 using polymer compound R-1-4 forcomparative examples comprising a repeating unit having a functionalgroup interacting with the substrate surface and a repeating unitcontaining a hydrophilic group having a zwitterionic structure in a sidechain but lacking a polymerizable group in a side chain of any repeatingunit was shown to be poor in staining resistance, and stainingresistance over time. Moreover, it was also shown to be inferior to theother Examples in the evaluation of developability and the number ofsheets developed on press. Comparative example 1-18 using polymercompound R-1-5 for comparative examples comprising a repeating unithaving a functional group interacting with the substrate surface and arepeating unit having a polymerizable group in a side chain of therepeating unit but lacking a specific linking group and not complyingwith formula (a1-1) was shown to be poor in staining resistance andstaining resistance over time. Further, it was also shown to be inferiorto the other Examples in the evaluation of the number of sheetsdeveloped on press.

Example C Synthesis Example of a Copolymer Synthesis Example 1 Synthesisof a Compound of the Present Invention (P-2-21)

(1) Synthesis of N-aminoethyl methacrylamide

To an ice-cooled solution of 24.04 g (0.4 mol) of ethylenediaminedissolved in 100 ml of methanol and 96 g of distilled water is added 104g (0.52 mol) of 5.0 M hydrochloric acid. While the temperature is keptat −10° C., 61.65 g of methacrylic anhydride is added dropwise, andafter completion of the dropwise addition, the mixture is stirred at−10° C. for 2 hours. Then, the mixture is extracted with ml of ethylacetate and the aqueous layer is collected. To the collected aqueouslayer is added 21 g (0.52 mol) of sodium hydroxide, and the precipitatedwhite crystals are removed by filtration and extracted with 400 ml ofacetonitrile. The acetonitrile solution is dried over 40 g of magnesiumsulfate for 2 hours, and then acetonitrile is distilled off to give 14.4g of N-aminoethyl methacrylamide (yield 28%).

(2) Purification of LIGHT ESTER P-2-1 Mby Separation

An aqueous solution of 40.0 g of LIGHT ESTER P-2-1M (from KyoeishaChemical Co., Ltd.) dissolved in 100 g of distilled water was purifiedby separation twice with 100 g of diethylene glycol dibutyl ether togive an aqueous solution of LIGHT ESTER P-2-1M (concentration 10.5% bymass).

(3) Polymerization

A 200-ml flask equipped with a condenser and a stirrer was charged with27.32 g of distilled water and heated to 55° C. under a stream ofnitrogen gas. A solution consisting of 0.71 g of N-aminoethylmethacrylamide synthesized above, 11.1 g of the aqueous solution ofLIGHT ESTER P-2-1M synthesized above, 3.87 g of 3-sulfonatopropyl[2-(methacryloyloxy)ethyl]dimethylammonium (from Aldrich), 0.32 g of thepolymerization initiator VA046B (from Wako Pure Chemical Industries,Ltd.), and 9.41 g of distilled water was added dropwise into the 200-mlflask over 2 hours. After completion of the dropwise addition, themixture was stirred at 55° C. for 2 hours, and 0.32 g of thepolymerization initiator VA046B (from Wako Pure Chemical Industries,Ltd.) was added, and the mixture was further stirred at 55° C. for 2hours to give a precursor for compound (21).To 50.0 g of an aqueous solution of the resulting precursor for compound(1) was added 1.38 g of sodium hydroxide and dissolved, and then thesolution was warmed to 40° C. and 4.3 g of Karenz MOI (from Showa DenkoK.K.) was added, and the mixture was stirred at 40° C. for 6 hours.Then, an aqueous solution obtained by removing precipitated whitecrystals by filtration was stirred with 8.83 g of Amberlyst R15 (fromAldrich) at room temperature for 2 hours, and then Amberlyst R15 wasremoved by filtration to give compound (P-2-21). The weight averagemolecular weight (Mw) of the resulting compound (P-2-21) was determinedto be 150,000 by Gel Permeation Chromatography (GPC) using polyethyleneglycol as standard. Further, the reaction yield of amino groups was 75%as determined by the color reaction of amino groups.

The compound used in this Example was synthesized by changing themonomer components of the repeating units in the Synthesis exampledescribed above, changing the type and amount of the reactive reagentused for amino substitution reaction, and further using an existingsynthesis method, if desired.

Example D (1) Preparation of Lithographic Printing Plate Precursors

The aluminum substrates used were aluminum substrates 1 to of Example B.A coating solution for primer layer 2 having the composition shown belowwas applied on each of the aluminum substrate 1 to 3 using a bar coaterand dried at 100° C. for 1 minute to form a primer layer. The coatingmass of the primer layer was 12 mg/m² in each case.

<Coating Solution for Primer Layer 2>

One of the copolymers of the present invention 0.50 g  described inTable 9 or Table 10 or the polymer compounds for comparison shown belowMethanol 450 g Pure water  50 g

[Formation of Photosensitive Layer 2-1]

A coating solution for photosensitive layer 2-1 having the compositionshown below was applied on the primer layer using a bar coater, and thendried in an oven at 90° C. for 60 seconds to form photosensitive layer2-1 having a coating mass of 1.3 g/m² after drying.

<Coating Solution for Photosensitive Layer 1>

Binder polymer (1) shown below (mass average molecular 0.34 g weight:50,000) Polymerizable compound (1) shown below 0.68 g (PLEX6661-O fromDegussa Japan Co., Ltd.) Sensitizing dye (1) shown below 0.06 gPolymerization initiator (1) shown below 0.18 g Chain transfer agent (1)shown below 0.02 g Dispersion of ε-phthalocyanine pigment 0.40 g(pigment: 15 parts by mass, dispersant (allyl methacrylate/ methacrylicacid copolymer (mass average molecular weight: 60,000, molar ratio:83/17)): 10 parts by mass, cyclohexanone: 15 parts by mass) Thermalpolymerization inhibitor 0.01 g (N-nitrosophenylhydroxylamine aluminumsalt) Fluorosurfactant (1) shown below (mass average molecular 0.001 gweight: 10,000) Polyoxyethylene-polyoxypropylene condensate 0.02 g(Pluronic L44 from ADEKA) Dispersion of yellow pigment 0.04 g (yellowpigment Novoperm Yellow H2G (from Clariant): 15 parts by mass,dispersant (allyl methacrylate/methacrylic acid copolymer (mass averagemolecular weight: 60,000, molar ratio: 83/17)): 10 parts by mass,cyclohexanone: 15 parts by mass) 1-Methoxy-2-propanol 3.5 g Methyl ethylketone 8.0 g Binder polymer (1)

Polymerizable compound (1)

Sensitizing dye (1)

Polymerization initiator (1)

Chain transfer agent (1)

Fluorosurfactant (1)

[Formation of Photosensitive Layer 1-2]

A coating solution for photosensitive layer 2-2 having the compositionshown below was applied on the primer layer using a bar coater, and thendried in an oven at 90° C. for 60 seconds to form photosensitive layer2-2 having a coating mass of 1.3 g/m² after drying.

<Coating Solution for Photosensitive Layer 2-2>

Binder polymer (1) shown above (mass average molecular 0.04 g weight:50,000) Binder polymer (2) shown below (mass average molecular 0.30 gweight: 80,000) Polymerizable compound (1) shown above 0.17 gPolymerizable compound (2) shown below 0.51 g Sensitizing dye (2) shownbelow 0.03 g Sensitizing dye (3) shown below 0.015 g Sensitizing dye (4)shown below 0.015 g Polymerization initiator (1) shown above 0.13 gChain transfer agent: mercaptobenzothiazole 0.01 g Dispersion ofε-phthalocyanine pigment 0.40 g (pigment: 15 parts by mass, dispersant(allyl methacrylate/ methacrylic acid copolymer (mass average molecularweight: 60,000, molar ratio: 83/17)): 10 parts by mass, cyclohexanone:15 parts by mass) Thermal polymerization inhibitor 0.01 g(N-nitrosophenylhydroxylamine aluminum salt) Fluorosurfactant (1) shownabove (mass average molecular 0.001 g weight: 10,000)1-Methoxy-2-propanol 3.5 g Methyl ethyl ketone 8.0 g

Sensitizing dye (2)

Sensitizing dye (3)

Sensitizing dye (4)

[Formation of Photosensitive Layer 2-3]

A coating solution for photosensitive layer 2-3 having the compositionshown below was applied on the primer layer 2 using a bar coater, andthen dried in an oven at 125° C. for seconds to form photosensitivelayer 2-3 having a coating mass of 1.4 g/m² after drying. The coatingsolution for photosensitive layer 2-3 was prepared by mixing thesensitizer solution (1) and hydrophobizing solution (1) shown below andstirring the mixture immediately before it was applied.

<Sensitizer Solution (1)>

Binder polymer (3) shown below 0.162 g IR absorber (1) shown below 0.030g Polymerization initiator (3) shown below 0.162 g Polymerizablecompound (ARONIX M215 from Toagosei 0.385 g Co., Ltd.) PIONIN A-20 (fromTAKEMOTO OIL & FAT Co., Ltd.) 0.055 g Oil-sensitizer (1) shown below0.044 g Fluorosurfactant (1) shown above 0.008 g Methyl ethyl ketone1.091 g 1-Methoxy-2-propanol 8.609 g

<Hydrophobizing Solution (1)>

Aqueous dispersion of hydrophobization precursor (1) 2.640 g prepared inExample B Distilled water 2.425 g

[Formation of protective layer 1]

It was formed by the same procedure as described for protective layer 1in Example B.

[Formation of Protective Layer 2]

It was formed by the same procedure as described for protective layer 2in Example B.

The aluminum substrates, copolymers (A) added to the coating solutionfor primer layer 2, coating solutions for photosensitive layer, andcoating solutions for protective layer described above were combined asshown in Table 9 and Table 10 below to prepare lithographic printingplate precursors of the present invention A-2-1 to A-2-35, andlithographic printing plate precursors for comparison B-2-1 to B-2-9.

TABLE 9 Coating liquid Coating liquid Lithographic for forming forforming printing plate Aluminum (A) photosensitive protective precursorsupport Copolymer layer layer A-2-1 1 P-2-1 2-1 1 A-2-2 1 P-2-1 2-1(*) 1A-2-3 1 P-2-2 2-1 1 A-2-4 1 P-2-3 2-1 1 A-2-5 1 P-2-4 2-1 1 A-2-6 1P-2-5 2-1 1 A-2-7 1 P-2-12 2-1 1 A-2-8 1 P-2-15 2-1 1 A-2-9 1 P-2-16 2-11 A-2-10 1 P-2-17 2-1 1 A-2-11 1 P-2-21 2-1 1 A-2-12 1 P-2-26 2-1 1A-2-13 1 P-2-28 2-1 1 A-2-14 1 P-2-30 2-1 1 A-2-15 1 P-2-33 2-1 1 A-2-161 P-2-44 2-1 1 A-2-17 1 P-2-45 2-1 1 A-2-18 1 P-2-47 2-1 1 A-2-19 1P-2-48 2-1 1 A-2-20 3 P-2-5 2-2 1 A-2-21 3 P-2-16 2-2 1 A-2-22 3 P-2-212-2 1 A-2-23 3 P-2-30 2-2 1 A-2-24 3 P-2-33 2-2 1 A-2-25 3 P-2-44 2-2 1A-2-26 3 P-2-45 2-2 1 A-2-27 3 P-2-47 2-2 1 (*)1: No primer layer wasapplied, but a photosensitive layer was formed by mixing a coatingsolution for primer layer containing copolymer (A) with a coatingsolution for photosensitive layer immediately before it was applied.

TABLE 10 Coating liquid Coating liquid Lithographic for forming forforming printing plate Aluminum (A) photosensitive protective precursorsupport Copolymer layer layer A-2-28 2 P-2-5 2-3 2 A-2-29 2 P-2-16 2-3 2A-2-30 2 P-2-21 2-3 2 A-2-31 2 P-2-30 2-3 2 A-2-32 2 P-2-33 2-3 2 A-2-332 P-2-44 2-3 2 A-2-34 2 P-2-45 2-3 2 A-2-35 2 P-2-47 2-3 2 B-2-1 1 R-2-12-1 1 B-2-2 1 R-2-2 2-1 1 B-2-3 1 R-2-3 2-1 1 B-2-4 3 R-2-1 2-2 1 B-2-53 R-2-2 2-2 1 B-2-6 3 R-2-3 2-2 1 B-2-7 2 R-2-1 2-3 2 B-2-8 2 R-2-2 2-32 B-2-9 2 R-2-3 2-3 2 B-2-10 1 R-2-4 2-1 1 B-2-11 1 R-2-5 2-1 1 B-2-12 3R-2-4 2-2 1 B-2-13 3 R-2-5 2-2 1 B-2-14 2 R-2-4 2-3 1 B-2-15 2 R-2-5 2-31

In Table 9 and Table 10 above, P-2-1, P-2-2, P-2-3, P-2-4, P-2-5,P-2-12, P-2-15, P-2-16, P-2-17, P-2-21, P-2-26, P-2-28, P-2-30, P-2-33,P-2-44, P-2-P-2-45, P-2-47, and P-2-48 shown in the column of copolymer(A) represent specific examples of copolymers containing (a0) arepeating unit having a structure represented by formula (a1-0) in aside chain. R-2-1 to R-2-5 are compounds for comparison havingstructures shown below. Compounds R-2-4 and R-2-5 shown below arecompounds (5) and (1-D), respectively of JP-A2008-265275.

(2) Evaluation of Lithographic Printing Plate Precursors [Exposure,Development and Printing]

Exposure, development and printing were performed by using variouslithographic printing plate precursors shown in Table 11 and Table 12below in the same manner as in Example B. The developer used was alsoany one of developers 1 to shown in Example B.

[Evaluation]

Each lithographic printing plate precursor was evaluated for printingdurability, staining resistance, developability, printing durabilitywith UV inks and chemical resistance as follows. The results are shownin Table 11 and Table 12.

<Printing Durability>

Printing durability was evaluated in the same manner as in Example B. InTable 11 and Table 12 below, the results were reported as the relativeprinting durability defined below using Examples 2-6 and 2-24 asreferences (1.0) respectively.

<Staining Resistance>

Staining resistance was evaluated in the same manner as in Example B.

<Developability>

Developability was evaluated in the same manner as in Example B. Theevaluation of developability was reported as the relative developabilitydefined below using Examples 2-6 and 2-24 as references (1.0)respectively in Table 11 and Table 12 below. Higher values of therelative developability indicate higher developability and betterperformance.

<Printing Durability with UV Inks>

In the evaluation of printing durability described above, the dampeningwater (EU-3 (an etching solution from FujifilmCorporation)/water/isopropyl alcohol=1/89/10 (volume ratio)) andTRANS-G(N) black ink (from DIC Corporation) were replaced by a 2 vol %aqueous solution of the dampening solution IF102 (from FujifilmCorporation) and BEST CURE UV-BF-WRO Standard Color Black ink (from T&KTOKA Co., Ltd.), and after the dampening solution and the ink weresupplied, printing was performed at a printing speed of 6000 sheets/hr.Printing durability with UV inks was evaluated by determining the numberof prints when the image density of a print decreased by 5% as comparedwith the density at the start of printing, and reported as the relativeprinting durability with UV inks defined below using Examples 2-6 and2-24 as references (1.0), respectively in Table 11 and Table 12. Highervalues of the relative printing durability with UV inks indicate higherprinting durability with UV inks.

Relative printing durability with UV inks=(Printing durability with UVinks of test lithographic printing plate precursor)/(Printing durabilitywith UV inks of reference lithographic printing plate precursor)

<Chemical Resistance>

In the evaluation of printing durability described above, the dampeningwater (EU-3 (an etching solution from FujifilmCorporation)/water/isopropyl alcohol=1/89/10 (volume ratio)) andTRANS-G(N) black ink (from DIC Corporation) were replaced by a 4 vol %aqueous solution of the dampening solution IF102 (from FujifilmCorporation) and Values G black ink (from DIC Corporation), and theplate surface was wiped with Multicleaner (from Fujifilm Corporation)every 5000 sheets. Printing was performed on a woodfree paper, andchemical resistance was evaluated by determining the number of printswhen the density of the solid image was visually observed to begin todecrease, and reported as the relative chemical resistance defined belowusing Examples 2-6 and 2-24 as references (1.0), respectively in Table11 and Table 12. Higher values of the relative chemical resistanceindicate higher chemical resistance.

Relative chemical resistance=(Chemical resistance of test lithographicprinting plate precursor)/(Chemical resistance of reference lithographicprinting plate precursor)

TABLE 11 Litho- Print- graphic ing print- Print- Stain- dura- Chem- inging ing bility ical plate Devel- dura- resis- Devel- with resis-precursor oper bility tance opability Inks tance Example 2-1 A-2-1 1 1 61 1 1 Example 2-2 A-2-2 1 1 6 1 1 1 Example 2-3 A-2-3 1 1 7 1 1 1Example 2-4 A-2-4 1 1 7 1 1 1 Example 2-5 A-2-5 1 1 7 1 1 1 Example 2-6A-2-6 1 1 8 1 1 1 Example 2-8 A-2-8 1 1 9 1 1.1 1 Example 2-9 A-2-9 1 19 1 1.1 1 Example 2-10 A-2-10 1 1.2 7 0.9 1.2 1 Example 2-11 A-2-11 1 19 1 1 1 Example 2-12 A-2-12 1 1 8 1 1 0.9 Example 2-13 A-2-13 1 0.9 8 10.9 1 Example 2-14 A-2-14 1 0.9 9 1 0.9 0.9 Example 2-15 A-2-15 1 1 9 11.1 1 Example 2-16 A-2-16 1 1 7 1 1 1 Example 2-17 A-2-17 1 0.8 8 1 0.80.8 Example 2-18 A-2-18 1 0.8 8 1 0.8 0.8 Example 2-19 A-2-19 1 0.8 8 10.8 0.8 Example 2-20 A-2-6 2 1 8 1 1 1 Example 2-21 A-2-15 2 1 9 1 1 1Example 2-22 A-2-6 3 1 8 1 1 1 Example 2-23 A-2-15 3 1 9 1 1 1Comparative B-2-1 1 0.9 4 0.6 0.9 0.9 Example 2-1 Comparative B-2-2 10.3 2 0.6 0.3 0.3 Example 2-2 Comparative B-2-3 1 0.9

0.8 0.9 0.9 Example 2-3 Comparative B-2-1 2 0.9 4 0.6 0.9 0.9 Example2-4 Comparative B-2-3 2 0.9 6 0.8 0.9 0.9 Example 2-5 Comparative B-2-13 0.9 4 0.6 0.9 0.9 Example 2-6 Comparative B-2-3 3 0.9 6 0.8 0.9 0.9Example 2-7 Comparative B-2-10 1 0.3 7 0.7 0.3 0.3 Example 2-17Comparative B-2-11 1 0.3 8 0.8 0.3 0.3 Example 2-18

indicates data missing or illegible when filed

TABLE 12 Litho- Print- graphic ing print- Print- Stain- dura- Chem- inging ing De- bility ical plate Devel- dura- resis- velop- with resis-precursor oper bility tance ability inks tance Example 2-24 A-2-20 4 1 91 1 1 Example 2-25 A-2-21 4 1.1 9 1 1 1 Example 2-26 A-2-22 4 1 9 1.2 11 Example 2-27 A-2-23 4 1 9 1 0.9 0.9 Example 2-28 A-2-24 4 1.1 9 1.1 11 Example 2-29 A-2-25 4 1 7 1 1 1 Example 2-30 A-2-26 4 0.8 8 1 0.8 0.8Example 2-31 A-2-27 4 0.8 9 1.1 0.8 0.8 Example 2-32 A-2-20 5 1 9 1 1 1Example 2-33 A-2-21 5 1.1 9 1 1 1 Example 2-34 A-2-22 5 1 9 1.2 1 1Example 2-35 A-2-23 5 1 9 1 0.9 0.9 Example 2-36 A-2-24 5 1.1 9 1.1 1 1Example 2-37 A-2-25 5 1 7 1 1 1 Example 2-38 A-2-26 5 0.9 6 1 0.9 0.9Example 2-39 A-2-27 5 0.8 9 1.1 0.8 0.8 Comparative B-2-4 4 0.9 3 0.50.9 0.9 Example 2-8 Comparative B-2-5 4 0.5 3 0.5 0.4 0.4 Example 2-9Comparative B-2-6 4 0.9 6 0.6 0.9 0.9 Example 2-10 Comparative B-2-4 50.9 2 0.4 0.9 0.9 Example 2-11 Comparative B-2-5 5 0.4 3 0.5 0.3 0.3Example 2-12 Comparative B-2-6 5 0.9 6 0.6 0.9 0.9 Example 2-13Comparative B-2-12 4 0.4 7 0.7 0.4 0.4 Example 2-19 Comparative B-2-13 40.4 8 0.8 0.4 0.4 Example 2-20

Table 11 and Table 12 above show that the lithographic printing plateprecursors using copolymers (A) of the present invention can providelithographic printing plates excellent in printing durability andprinting durability with UV inks without compromising stainingresistance and developability. Moreover, the lithographic printing plateprecursors of the present invention were also excellent in chemicalresistance. Among the lithographic printing plate precursors of thepresent invention, A-2-1 to A-2-16, A-2-18 to A-2-29, A-2-31 to A-2-37and A-2-39 were shown to especially strike an excellent balance amongprinting durability, staining resistance, developability and printingdurability with UV inks, and the lithographic printing plates obtainedtherefrom were also shown to provide an excellent balance among printingdurability, staining resistance, developability, printing durabilitywith UV inks and chemical resistance. In Example 2-7, printingdurability, staining resistance, printing durability with UV inks, andchemical resistance were evaluated by using lithographic printing plateA-2-7 and developer 1 to find that they were good.

However, the polymer compounds for comparative examples comprising aside chain repeating unit lacking a specific linking group and notcomplying with formula (a1-1) did not produce advantages of the presentinvention. Specifically, Comparative examples 2-1, 2-4, 2-6, 2-8 and2-11 using polymer compound R-2-1 for comparative examples were shown tobe poor in staining resistance and developability. Comparative examples2-2, 2-9 and 2-12 using polymer compound R-2-2 for comparative exampleswere shown to be poor in printing durability, staining resistance,developability and printing durability with UV inks even though thispolymer compound R-2-2 comprises a repeating unit having a functionalgroup interacting with the substrate surface.Comparative examples 2-3, 2-5, 2-6, 2-10 and 2-13 using polymer compoundR-2-3 for comparative examples were shown to be poor in developability.The comparative examples using polymer compounds R-2-4 and R-2-5 forcomparative examples were shown to be poor in printing durability,printing durability with UV inks, and chemical resistance.

[Exposure, Development and Printing]

Various lithographic printing plate precursors shown in Table 13 belowwere image-exposed using Trendsetter 3244VX from Creo (incorporating awater-cooled 40 W infrared semiconductor laser) under conditions of anoutput power of 9 W, an external drum rotational speed of 210 rpm, and aresolution of 2,400 dpi. Within 30 seconds after then, the precursorswere preheated at 100° C. for 30 seconds, and then developed usingdeveloper 1 in the same manner as in

Example B

The lithographic printing plates obtained were used to evaluate printingdurability, staining resistance, developability, printing durabilitywith UV inks and chemical resistance in the same manner as in Example B.Example 2-40 was used as a reference for relative evaluations. Theresults are shown in Table 13 below.

TABLE 13 Litho- Print- graphic ing print- Print- Stain- dura- Chem- inging ing De- bility ical plate Devel- dura- resis- velop- with resis-precursor oper bility tance ability Inks tance Example 2-40 A-2-28 1 1 91 1 1 Example 2-41 A-2-29 1 1 9 1 1 1 Example 2-42 A-2-30 1 1 9 1.2 1 1Example 2-43 A-2-31 1 0.9 9 1.1 0.9 0.9 Example 2-44 A-2-32 1 1 9 1.2 11 Example 2-45 A-2-33 1 1 7 1 1 1 Example 2-46 A-2-34 1 0.9 7 1 0.9 0.9Example 2-47 A-2-35 1 0.8 9 1.1 0.8 0.8 Comparative B-2-7 1 0.9 4 0.60.9 0.9 Example 2-14 Comparative B-2-8 1 0.3 5 0.5 0.3 0.3 Example 2-15Comparative B-2-9 1 0.9 7 0.7 0.9 0.9 Example 2-16 Comparative B-2-14 10.3 7 0.7 0.3 0.3 Example 2-21 Comparative B-2-15 1 0.3 8 0.8 0.3 0.3Example 2-22

Table 13 above show that the lithographic printing plate precursorsusing copolymers (A) of the present invention can also providelithographic printing plates excellent in printing durability, printingdurability with UV inks and chemical resistance without compromisingstaining resistance and developability when they were image-exposedusing infrared light. Moreover, the lithographic printing plateprecursors of the present invention were also excellent in chemicalresistance. Among the lithographic printing plate precursors of thepresent invention, Examples 2-40 to 2-45 and 2-47 were shown toespecially strike an excellent balance among printing durability,staining resistance, developability and printing durability with UVinks, and the lithographic printing plates obtained therefrom were alsoshown to provide an excellent balance among printing durability,staining resistance, developability, printing durability with UV inksand chemical resistance.

However, the polymer compounds for comparative examples comprising aside chain repeating unit lacking a specific linking group and notcomplying with formula (a1-1) did not produce advantages of the presentinvention. Specifically, Comparative example 2-14 using polymer compoundR-2-1 for comparative examples was shown to be poor in stainingresistance and developability.Comparative example 2-15 using polymer compound R-2-2 for comparativeexamples was shown to be poor in printing durability, stainingresistance, developability and printing durability with UV inks.Comparative example 2-16 using polymer compound R-2-3 for comparativeexamples was shown to be poor in developability. The comparativeexamples using polymer compound R-2-4 or R-2-5 for comparative exampleswere shown to be poor in printing durability, printing durability withUV inks, and chemical resistance.

LEGENDS

-   -   4: Lithographic printing plate precursor    -   6: Developing part    -   10: Drying part    -   16: Feed roller    -   20: Developer tank    -   22: Feed roller    -   24: Brush roller    -   26: Squeeze roller    -   28: Backup roller    -   36: Guide roller    -   38: Segmented roller    -   11: Feed path for lithographic printing plate precursor    -   100: Automatic developing machine    -   200: Preheating part    -   300: Developing part    -   400: Drying part    -   202: Casing    -   208: Heating chamber    -   210: Segmented roller    -   212: Inlet    -   214: Heater    -   216: Circulation fan    -   218: Outlet    -   304: Feed-in roller pair    -   306: Process tank    -   308: Developer tank    -   310: Outer panel    -   312: Feed-in slot    -   316: Submerged roller pair    -   318: Feed-out roller pair    -   322: Brush roller pair    -   324: Shield cover    -   326: Brush roller pair    -   330: Spray pipe    -   332: Partition panel    -   334: Feed-through slot    -   336: Liquid temperature sensor    -   338: Liquid level meter    -   332: Partition panel    -   342: Guide member    -   344: Guide roller    -   402: Support roller    -   404: Exit    -   406: Feed roller pair    -   408: Feed roller pair    -   410: Duct    -   412: Duct    -   414: Slit opening    -   50: External tank    -   51: Overflow vent    -   52: Upper limit indicator    -   53: Lower limit indicator    -   54: Filter part    -   55: Developer feed pump    -   C1: First circulation pipe    -   C2: Second circulation pipe    -   71: Tank for replenishing water    -   72: Water replenishing pump    -   C3: Third circulation pipe

What is claimed is:
 1. A lithographic printing plate precursorcomprising: a substrate; a photosensitive layer provided on thesubstrate; and an extra layer optionally provided between the substrateand the photosensitive layer; wherein the photosensitive layer or theextra layer adjacent to the substrate contains (A) a copolymer; andwherein the copolymer (A) comprises: (a1) a repeating unit having astructure represented by formula (a1-1) below in a side chain, and (a2)a repeating unit having at least one of the structure represented byformulae (a2-1) and (a2-2) below in a side chain;

in formula (a1-1), L¹ represents a single bond, a divalent aromaticgroup containing 6 to 14 carbon atoms, —C(═O)—O—, or —C(═O)—NR²—(wherein R² represents a hydrogen atom, alkyl or aryl); Z¹ representsmethylene, ethylene, propylene, butylene, pentylene, hexylene,heptylene, octylene, cyclohexane-1,4-diyl, 1,2-phenylene, 1,3-phenylene,1,4-phenylene, 1,2-naphthalene, 1,5-naphthalene and a linking groupcomposed of two or more of these divalent linking groups linked through—O— or —S—, wherein a hydrogen atom in these divalent linking groups maybe replaced by substituents; R¹ represents a hydrogen atom, alkyl, aryl,heterocyclyl, sulfo, alkylsulfonyl and arylsulfonyl; R²¹, R²² and R²³each independently represent a hydrogen atom, halogen atom or C1-8alkyl; the asterisk (*) indicates the point of attachment to the mainchain of the copolymer;

in formula (a2-1) or (a2-2), M¹ to M⁴ each independently represent ahydrogen atom, a metal atom contained in an alkali metal or an alkalineearth metal or ammonium; Y²¹ or Y²² represent a single bond, or adivalent linking group selected from the group consisting of —CO—, —O—,—NH—, a divalent aliphatic group, a divalent aromatic group and acombination thereof; and the asterisk (*) indicates the point ofattachment to the main chain of the polymer compound.
 2. Thelithographic printing plate precursor according to claim 1, wherein Z¹in formula (a1-1) above is a group selected from group A below or acombination thereof; (Group A)

in group A, R⁵², R⁵³ and R⁵⁶ each independently represent a hydrogenatom, halogen atom, hydroxyl, alkoxy, alkyl, aryl or cyano; R⁵⁶ eachindependently represents a halogen atom, hydroxyl, alkoxy, alkyl, arylor cyano, n each independently represents an integer of 0 to 4, and mrepresents an integer of 0 or 1; if a plurality of R⁵⁶ groups exist,they may be identical or different.
 3. The lithographic printing plateprecursor according to claim 1, wherein the photosensitive layercontains (B) a polymerization initiator, (C) a polymerizable compound,(D) a binder and (E) a dye.
 4. The lithographic printing plate precursoraccording to claim 1, wherein the copolymer (A) is contained in theextra layer.
 5. The lithographic printing plate precursor according toclaim 1, wherein Z¹ in formula (a1-1) above is a group selected fromgroup B below or a combination thereof; (Group B)

in group B, R⁵¹ and R⁵² each independently represent a hydrogen atom,halogen atom, hydroxyl, alkoxy, alkyl, aryl or cyano.
 6. Thelithographic printing plate precursor according to claim 1, wherein Z¹in formula (a1-1) above is C1-14 alkylene, or a divalent linking grouphaving a linking chain length of 1 to 14 atoms and composed of two ormore alkylenes linked through an oxygen atom linking group (wherein thealkylenes may each independently be substituted).
 7. The lithographicprinting plate precursor according to claim 1, wherein the M¹ to M⁴represent a hydrogen atom in formula (a2-1) above and formula (a2-2)above.
 8. The lithographic printing plate precursor according to claim1, wherein the copolymer (A) further comprises (a3) a repeating unithaving a hydrophilic group in a side chain.
 9. The lithographic printingplate precursor according to claim 8, wherein the hydrophilic groupcontained in the repeating unit (a3) having a hydrophilic group in aside chain is a group having a zwitterionic structure represented byformula (a3-1) or formula (a3-2) below:

in formula (a3-1), R³¹ and R³² each independently represent a hydrogenatom, alkyl, alkenyl, alkynyl, aryl, or heterocyclyl, or R³¹ and R³² maybe joined together to form a ring structure, L³¹ represents a linkinggroup, and A represents an anion-containing structure; Y³ represents asingle bond, or a divalent linking group selected from the groupconsisting of —CO—, —O—, —NH—, a divalent aliphatic group, a divalentaromatic group and a combination thereof; the asterisk (*) indicates thepoint of attachment to the main chain of the copolymer;

in formula (a3-2) above, L³² represents a linking group, and E⁺represents a cation-containing structure; Y⁴ represents a single bond,or a divalent linking group selected from the group consisting of —CO—,—O—, —NH—, a divalent aliphatic group, a divalent aromatic group and acombination thereof; the asterisk (*) indicates the point of attachmentto the main chain of the copolymer.
 10. The lithographic printing plateprecursor according to claim 9, wherein the group having a zwitterionicstructure is represented by formula (a3-1) above.
 11. The lithographicprinting plate precursor according to claim 9, wherein A⁻ in formula(a3-1) above is sulfonate.
 12. A process for preparing a lithographicprinting plate, comprising: image-exposing a lithographic printing plateprecursor according to claim 1; and developing the exposed lithographicprinting plate precursor in the presence of a developer having a pH of 2to 14 to remove the photosensitive layer in unexposed areas.
 13. Theprocess for preparing a lithographic printing plate according to claim12, comprising forming a protective layer on the surface of thephotosensitive layer opposite to the substrate; wherein the developingcomprises removing the photosensitive layer in unexposed areas and theprotective layer simultaneously in the presence of the developer furthercontaining a surfactant without including water-washing.
 14. The processfor preparing a lithographic printing plate according to claim 12,comprising controlling the pH of the developer at 2.0 to 10.0.
 15. Aprocess for preparing a lithographic printing plate, comprising:image-exposing a lithographic printing plate precursor according toclaim 1; and supplying a printing ink and a dampening solution on aprinting press to remove the photosensitive layer in unexposed areas.16. A copolymer comprising: (a1) a repeating unit having a structurerepresented by formula (a1-1) below in a side chain; (a2) a repeatingunit having at least one of the structures represented by formulae(a2-1), (a2-2), (a2-3), (a2-4), (a2-5) and (a2-6) in a side chain; and(a3′) a repeating unit having a zwitterionic structure represented byformula (a3-1) or (a3-2) below in a side chain;

in formula (a1-1), L¹ represents a single bond, a divalent aromaticgroup containing 6 to 14 carbon atoms, —C(═O)—O—, or —C(═O)—NR²—(wherein R² represents a hydrogen atom, alkyl or aryl); Z¹ represents adivalent linking group selected from the group consisting of a divalentaliphatic group containing 1 to 14 carbon atoms, a divalent aromaticgroup containing 6 to 14 carbon atoms, —NH—, —O—, —S— and a combinationthereof, provided that both ends are not —NH—, —O— or —S—, and when L¹is a divalent aromatic group containing 6 to 14 carbon atoms, Z¹ is nota divalent aromatic group containing 6 to 14 carbon atoms, and thedivalent aliphatic group, divalent aromatic group and —NH— may have asubstituent instead of a hydrogen atom; R¹ represents a hydrogen atom,alkyl, aryl, heterocyclyl, sulfo, alkylsulfonyl and arylsulfonyl; R²¹,R²² and R²³ each independently represent a hydrogen atom, halogen atomor C1-8 alkyl; the asterisk (*) indicates the point of attachment to themain chain of the copolymer;

wherein M¹ to M⁸ each independently represent a hydrogen atom, a metalatom contained in an alkali metal or an alkaline earth metal orammonium; R⁴¹ to R⁴⁶ each independently represent a hydrogen atom oralkyl; Y²¹ to Y²⁶ represent a single bond, or a divalent linking groupselected from the group consisting of —CO—, —O—, —NH—, a divalentaliphatic group, a divalent aromatic group and a combination thereof;the asterisk (*) indicates the point of attachment to the main chain ofthe polymer compound;

in formula (a3-1), R³¹ and R³² each independently represent a hydrogenatom, alkyl, alkenyl, alkynyl, aryl, or heterocyclyl, or R³¹ and R³² maybe joined together to form a ring structure, L³¹ represents a linkinggroup, and A represents an anion-containing structure; Y³ represents asingle bond, or a divalent linking group selected from the groupconsisting of —CO—, —O—, —NH—, a divalent aliphatic group, a divalentaromatic group and a combination thereof; the asterisk (*) indicates thepoint of attachment to the main chain of the polymer compound;

in formula (a3-2) above, L³² represents a linking group, and E⁺represents a cation-containing structure; Y⁴ represents a single bond,or a divalent linking group selected from the group consisting of —CO—,—O—, —NH—, a divalent aliphatic group, a divalent aromatic group and acombination thereof; the asterisk (*) indicates the point of attachmentto the main chain of the polymer compound.
 17. The copolymer accordingto claim 16, wherein Z¹ in the repeating unit having a structurerepresented by formula (a1) above is selected from group A below: (GroupA)

in group A, R⁵¹ to R⁵⁵ each independently represent a hydrogen atom,halogen atom, hydroxyl, alkoxy, alkyl, aryl or cyano; R⁵⁶ eachindependently represents a halogen atom, hydroxyl, alkoxy, alkyl, arylor cyano, n each independently represents an integer of 0 to 4, and mrepresents an integer of 0 to 2; if a plurality of R⁵⁶ groups exist,they may be identical or different.
 18. The copolymer according to claim16, wherein Z¹ in the repeating unit having a structure represented byformula (a1) above is selected from group B below: (Group B)

in group B, R⁵¹ to R⁵³ each independently represent a hydrogen atom,halogen atom, hydroxyl, alkoxy, alkyl, aryl or cyano.
 19. The copolymeraccording to claim 16, wherein the repeating unit (a2) has a side chainof a structure represented by formula (a2-1) above or formula (a2-2).20. The copolymer according to claim 16, wherein the side chain having azwitterionic structure in the repeating unit (a3′) is a structurerepresented by formula (a3-1) above.
 21. The copolymer according toclaim 16, wherein A⁻ in formula (a3-1) above is sulfonate.
 22. A processfor preparing the copolymer according to claim 16, comprisingintroducing the repeating unit (a1) having a structure represented byformula (a1-1) above in a side chain by reacting a polymer comprising:(a0) a repeating unit having a structure represented by formula (a1-0)below in a side chain; (a2) the repeating unit having a structuresrepresented by any one of formulae (a2-1), (a2-2), (a2-3), (a2-4),(a2-5) and (a2-6) above in a side chain; and (a3′) the repeating unithaving a zwitterionic structure represented by formula (a3-1) or (a3-2)above in a side chain; with a compound represented by formula (b-1) or(b-2) below;

in formula (a1-0), L¹⁰¹ represents a single bond, a divalent aromaticgroup containing 6 to 14 carbon atoms, —C(═O)—O—, or —C(═O)—NR¹⁰²—(wherein R¹⁰² represents a hydrogen atom, alkyl or aryl); Z¹⁰¹represents a divalent linking group selected from the group consistingof a divalent aliphatic group containing 1 to 14 carbon atoms, adivalent aromatic group containing 6 to 14 carbon atoms, —NH—, —O—, —S—and a combination thereof, provided that both ends are not —NH—, —O— or—S—, and when L¹ is a divalent aromatic group containing 6 to 14 carbonatoms, Z¹ is not a divalent aromatic group containing 6 to 14 carbonatoms, and the divalent aliphatic group, divalent aromatic group and—NH— may have a substituent instead of a hydrogen atom; R¹⁰¹ representsa hydrogen atom, alkyl, aryl, heterocyclyl, sulfo, alkylsulfonyl andarylsulfonyl; the asterisk (*) indicates the point of attachment to themain chain of the copolymer;

in formulae (b-1) and (b-2), R¹¹¹ represents a halogen atom, anoptionally substituted C1-8 alkoxy, or —OSOR¹¹²; R¹¹² represents anoptionally substituted C1-8 alkyl; R¹²¹ to R¹²⁹ each independentlyrepresent a hydrogen atom, halogen atom or C1-8 alkyl.